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Discussion Starter · #1 ·
Wondering if anyone has any recommendations on brand and weight of oil for my specific situation. I have a '73 GT with what I believe is the original 1.9L with 198,000 miles, pretty much all stock. Not sure if it was ever rebuilt. It smokes when you start it, so the rings are probably worn. Plus it leaks in a number of places...bad gaskets I suppose. I probably add one or two quarts per 1000 miles.

My goal is to get about another 20K - 30K out of this engine with as little expense as possible before rebuilding or replacing the engine. I've ruled out synthetic because of the cost and concerns about using it in such an old engine (I've heard it can actually be harmful). I used Castrol GTX 5W30 when I got it out of storage because I had some left over (I use it in my low mileage Caddy). I will be changing it again in 500-1000 miles because of the fact it's just out of storage, so I thought I'd get opinions first.
 

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I am interested what synthetic oil will do to a higher mileage engine. My 72 GT has 111,203 on it now, I just got it with 109,811. It was a 1,000 mile drive home, right before I left, it had Mobile 1 synthetic oil put into it. There were no obvious leaks between the head and block before I left, about 4/5 of the way home I had to add a quart of oil and since then it hasn't dropped, much anyway. But now it has leaks between the head and block towards the timing cover, and the timing cover leaks too now. Coincedence or cause and affect? The valve cover doesn't seem to be leaking though. Did synthetic oil cause this engine to start leaking, and if so what else can I expect, should I put regular oil back into it? BTW, the engine seems real good except for the low c/r for that year.
 

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One of the first things I ask about a car I'm about to purchase is "what kind of oil are you using?". I found out the hard way changing oil brands CAN cause oil leaks. For sure, using Castrol in a car the first time will cause leaks. It and the synthetics will clean the crud inside the engine away from the sealing surfaces and leaks will occur. Once the engine is rebuilt and Castrol is used from the start, there will not be any leaks if the engine is put together right. I don't know if others have had this problem, but I have on more than one car. Just my $.02

Ron
 

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Discussion Starter · #4 ·
Synthetic oil and older engines

My comments about synthetic oil and older engines come from a few different things I've read on the net. I have never used synthetic oil myself, although I plan to once I have an engine that can handle it.

I did some searching, and the only thread I could find off-hand about it is here:

http://www.opelgt.com/forums/showthread.php?s=&threadid=560
 

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Discussion Starter · #5 ·
Ron,

After your comments about Castrol, I'm a little worried about the fact that I used it. The PO didn't actually change the oil, since he never had it running in the two years he owned it. It was pretty much sitting the entire time before I bought it from him, and he didn't know what oil was used in it before. I just switched to my preferred brand at that time. I'd say it has had a total of 2000 miles on it since I've owned it. I bought it in '96, got it running and drove it until '99, then put it in storage because I moved. Now I'm just getting it out again.

So, basically I have no way of knowing what was used in it before, and have had Castrol in it for about 2000 miles. I can't say if it's been leaking worse or not since I've had it...it's hard to tell.

Is it better to stick with the Castrol at this point, or switch to something else? I've heard that for some reason, if you don't know the previous oil brand, it's safest to use Valvoline. I never knew whether to believe that or not.

Though it may be too late for me, when the previous brand is unknown, what is a good choice to start with?
 

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My daily driver (non-Opel) has 196,000 miles on it. The rear main seal started to leak (bad) at 160k or so, and it burns some oil as well. I started using Kendall 20-50 oil and now it leaks just a trickle. It uses about 3/4 quart per 5k now, and oil pressure at idle is almost double what it was with 10-40. Most of the local NASCAR modified-tour engine builders swear by the stuff, FWIW.

Bob
 

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The problem with Kendall is availability. One of the local hardware stores used to carry it but they don't any more. None of the 1/2 dozen or so auto parts stores I frequent carry it. I can get Amsoil and Redline easier than Kendall....:(

Where ever Bob is getting it in CT may be the closest place for me....

-Travis
 

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I always ran the Castrol 20-50 in the old British stuff...it still leaked ....just slowly....I feel the clearences on the older engines need the heavier weight. Of course, I live in the south. Up north 20/50 could be a problem.

I currently have conventional oil in the GT......I plan to switch to synthetic once I get enough miles on it to be sure the rings are seated. I'll use either Mobil 1 or Castrol Syntec. I have had good lunk with both.

Jc
 

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brand loyalty

You've got lots of opinions on oil, but I've always subscribed to the theory that sticking with one brand is always the best. While every oil is supposed to be compatable with every other oil, sometimes the additives in one don't get along well with the additives from another. Usually this is noticed when switching owners and the new owner adds a different oil for the first time.

That being said, I always use Castrol myself. You've got the super inexpensive stuff like Havoline, Penzoil or the gas station brand that I don't bother with, then the mid-priced stuff like Castrol, valvoline, and Quaker State. On top is the Red-line, Kendal, and Amsoil, nice if you can get it. I basically just picked one of the mid ones I could always get and stick with it, and I've had great luck. But the usual fall-out of a new old car purchase is a ritualistic round of gasket changeout as the Penzoil crud gets washed away.

There also used to be a lot of concern with too much difference in weight of the oil blend making oil not so stable in the long term. The fall-out at the time was that the oils with less than 30 weight difference were more stable than the ones with more separation. By this I mean that a 10/30 is more stable than a 10/40. A lot of people called this bunk, though, so maybe it is. Some of the old-timers used this as proof that straight 30W is still the best.

With a higher mileage engine, I would call 10/30 the absolute minimum, 10/40 the norm, and 20/50 the preferred option, particularly for summer time. The thicker oil just works better when there is more "slop" in the motor, and 5/30 is really an economy oil for tight motors and not intended for old motors. Straight 30W is another viable option, but not if it gets very cold where you are.
 

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Travis said:
The problem with Kendall is availability. One of the local hardware stores used to carry it but they don't any more. None of the 1/2 dozen or so auto parts stores I frequent carry it. I can get Amsoil and Redline easier than Kendall....:(

Where ever Bob is getting it in CT may be the closest place for me....

-Travis
Hmmm, this can definitely be a problem, I guess I'm 'lucky' in that most of the local auto parts stores (including NAPA) have it or can get it. It doesn't hurt that the New England distributor is in Hartford, and they will sell direct to the public. The only oil I can't get locally is the Redline, although they sell it at Lime Rock 28~ miles away...

What really sucks is that lately the bigger oil companies are all reformulating their oil, and not necessarily for the better. They're doing it for profitability. Mobil reformulated their 'Mobil 1' synthetics last year, and all the test results I've seen indicate it's not as good as it was before...som racing friends of mine started stockpiling the 'old' formula when they heard the new stuff was not as good. Castrol 'Syntec' is no longer 100% synthetic, regardless of what they may tell you, but the price stayed the same....
Even the Kendall 50 weight oil, which was a staple of racers everywhere, is no longer the trademark green color, and it seems to have lost some of its' viscocity in the process.

Money makes the world go 'round....:(

Bob
 

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A couple of things from Aircraft and Powerplant school may help here. The multi-grade oils are rated by their flow at certain standard temperatures. The lower number indicates the flow at 0 degrees, and the upper number is the flow or viscosity index at a temperature of 200 degrees, that's if memory serves me. Under a microscope the standard oils do not have a symetrical cell make-up, they are kinda raggedy, where sythentic oils are molecularly structured and are totally symetrical. Whether this causes a sandblast affect in the sealing surfaces I can't say, but the detergent action of different oils definately caused me problems. Specifically at the front and rear main seals and valve covers. Usually about 5-10,000 after I changed brands of oil to my preferred brand and weight. Castrol XL 20-50. I started using this oil in when I was racing motorcycles and at the end of the season when I toredown the engines, there was no carbon build-up anywhere, so no major cleaning was needed to rebuild the engines, just wipe them down and put them back together. That and I don't need the lower numbers here in sunny SoCal, but I do prefer the higher viscosity when I drive fun on the freeways. Just my $.02

Ron
 

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As far as conventional oils go these days........ There is NO difference between brands, except attive packages. Years ago, there WAS a difference between Pennsylvania Grade Crude and Texas Grade Crude. But now a days motor oil is made fron NEITHER. Also the cracking process is MUCH more sophisticated which yields a far superior oil than was available in the 70's and 80's.

So the effects of changing brands (convention to conventional; same grade to same grade) are nonexistant.

Our Opel engines were designed around the Viscosity of 10w-40 oil. 20w-50 is a thicker oil and will leak less. On a tight engine it will rob a few horse power. On a worn engine is will help reduce oil consumption.

A true synthetic oil (RedLine, Moble One, and Amsoil) are lighter in Viscosity and will reduce horse power loss. However, they are sooo slippery and have higher load bearing capacity they can be used in the place of thicker oils.

Near synthetics, (Synetc being one) are conventional oils were made from clear base stocks utilizing the Hydro-Cracking process. They are very good oils that meet the minimums requirements of synthetic, and therefore can carry the Synthetic Lable. This was decided in a court case about 5 years ago.

BTW, On my racing Neon, I run nothing but Synthetic (Moble One or RedLine).

Sorry for the long response. But it could have been longer

Paul
 

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Discussion Starter · #13 ·
Thanks for all the responses. Based on what I've heard so far, I may just stick with the Castrol since I don't know what was in it before, but switch to 20W50 to see if it helps the leaks. I don't have to worry about low temps here in SoCal, so I should be safe with the heavier oil.

It always seems like there are a lot of opinions when asked which oil is best, though it seems like a common theme about not switching brands, and I've always tried to stick with the same brand. Paul's post is an interesting opinion opposing that, though. I have to be honest that most of the opinions I've heard in the past come from guys who worked on cars in the 50's, 60's, and 70's. Curious to see if anyone else feels that things have changed as Paul does.
 

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Discussion Starter · #14 ·
Another related request for opinions deals with oil additives such as Rislone. My engine occasionally gets a sticky lifter. It's not a big deal (i.e. it doesn't cause a misfire, just gets noisier). In the past I have used Rislone 2-3 times to attempt to quiet it. I'm not necessarily proud of that, but I did it.

My dad, whose opinion I always respected, was very much against oil additives, but he actually agreed with me this time since the engine was so old and I'm basically just trying to hold it together for a year or two. He'd never use it in a decent engine. It's kind of like a patch-job as a last resort to hold together a frail engine until I can afford to do the right thing.
 

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synthetic oil

So... let's say some knucklehead put synthetic in a GT with 110,xxx+ miles and his engine started leaking where before it did not leak oil more than but a drip or two. Should this person go back to non-synthetic before it's too late? Just asking for an opinion more expeienced than my own.:eek:
 

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Now that, I can't say. I do know when I changed my oil in the monza to Castrol, within a couple of months, both main seals started leaking and the valve covers too. I changed the valve cover gaskets and the front main, twice. Now all I have leaking is the rear main. In order to change the rear main, I have to drop the pan and the rear main bearing cap, so I'm waiting until I get the GT mod finished. I just have to live with checking the oil before each outing, even though I change oil every 2000 miles in all my stuff, depending on the time/miles I may lose enough oil to be detrimental to the engine. Should the person change back to regular oil, I don't know, it could be the gaskets/seal surfaces are already opened or cleaned that they won't seal at all. Hard to say.

Ron
 

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If an engine, transmission , gear box, or etc leaks a little with the conventional specified lubricant, it will leak MORE if changed to synthetic. Why, you ask? Because of the lower viscosity/smaller molecules. The smaller molecules are able to squeeze out thru gaps and cracks easier than thicker oils.

I recently rebuilt the seals and gaskets on my Manta's 4-Speed tranny so that I can switch to RedLine MT-90 synthetic. It did leak some around the shifter shaft seals and out the rear as well. If I had simply put in synthetic, it would have leaked more.

What I know about lubrication (automotive and industrial) I learned from a reputable lubrication specalist and chemist. And what I know, is that the oils that meet todays standards are about 100 times better than oils from the 1970's and so are the additive packages. Remember, its not the oil that wears out, its the additives. So the better the oil, the less is reliance on the additives, especially the vicosity index improvers. This is where the grade of oil of the 1970's. especially the of 10w-40, had problems. The VI improvers could not handle the high levels of combustion by products and raw gas and would prematurly break down. This is where and why people started changing their oils at greatly shortened intervals.

Now days with computer controled fuel injection and exacting machining tolerances, ultra short change intervals are just of waste of oil, money and time.

Sorry I could write volumes. I have a very strong opinion based upon many facts and studies. Now Its time for me to get off my soap box, I hope I haven't offended anyone. (unless you happen to work for the marketing department for one of the major oil producers....

Paul

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All base stocks in conventional oils are not equal. They depend on the source of the oil (which well they came out of ) and the degree of refining they are put through. Some base stocks have good natural solvancy (detergency) but poor oxidation stability (temperature stability). Others have exactly the opposite characteristics. Additive packages are blended with the oil to compensate for characteristics missing in the base stock and to add others (such as antiwear characteristics), that are not found in any base stocks. The most common additive is a long chain polymer called a VI improver (viscosity index improver). It's purpose is to keep oils from thickening when cold and thinning when hot. i.e. the viscosity vs. temperature curve will be flatter. Synthetic oils made with with PAO's (poly alfa oelfins), such as Mobil 1, have naturally high VI's and excellent oxidation stability, consequently these oils have significantly fewer additives. Synthetic oils made with PAO base stocks do not cause an engine to leak. They will not deteriorate seals; however, because of their excellent low temperature flow characteristics they may leak through existing gaps in seals easier than a petroleum based product, especially when compared at lower temperatures.

Be careful using any 20W-? non synthetic products where temperatures below 40 degrees may be encountered. They don't flow well at low temperatures and can cause vital engine parts to be starved of oil.

I would recommend Mobil 1 in any vehicle regardless of the number of miles. If leakage is a concern use the highest viscosity possible for your expected climate. You can buy a lot of synthetic oil for the price of an engine rebuild!
 

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Which oil for my setup?

This thread is very interesting with great insight. I would like to ask for some suggestions : I have a 2.4 CIH (+/-1990 Omega) with approximately 80K miles and i have no idea what oil was used before. I have done work on the head an it has a new head gasket but timing cover was not touched and does not appear to be leaking as well as the front/rear main seals. The information until now suggests using Synthetic Oil but i wonder about a "Synthetic blend" such as Castrol Syntec, would this be good option instead of pure Synthetic? BTW, my brother has a freshly rebuilt 2.4 (4K miles)and uses Castrol Synthetic Blend and he has had no probems. I am ready to put the engine in the car and would appreciate your suggestions.
Thanks
Mauri
 

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Synthetic blends are exactly that, they're a blend between synthetic and petroleum. The idea is to capture many of the benefits of a synthetic at a lower than synthetic price. I've never been a fan of the blends. Oil is cheap, even synthetic oil. If you drive your car 15000 miles a year and change the oil every 5000 miles you will spend approximately:

3 qts of Mobil 1 $13.50 3 qts of Conventional oil $4.50
1 filter $ 3.00 1 filter $3.00
Total $16.50 Total $7.50

3 changes/year $49.50 $22.50

A savings of $27.00 per year is nothing compared to the added protection synthetic oil provides your engine. Compare that with a $2000 rebuild.
 
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