Gear Lube

[srthom13]

I have been a user of Mobil 1 ( both engine oil & gear lube ) for many years, both in my truck and in the vette. Over the years I felt that paying more than double the normal price of Dino oil was worth it - just for the technology invested by Mobil and maybe because they knew more than me. Oddly enough I could not brake my old habits and changed the synthetic on the same schedule as the Dino. I guess I just felt better with the synthetic in there. I know it is more slippery than Dino and has better hot and cold properties but what actually is Synthetic oil. Is it just regular Dino oil that has been Hydroprocessed ( fancy word used by Mobil to confuse us ) and than it is fortified with the normal chemical additives like the regular oils. I do not know but I still use it. Maybe, I, like many other people feel that if we are paying more it must be better. Anyway, the reason for this thread is that during the restoration of my 66 I removed the M21 trans and brought it in to a manual only trans shop for a check up. This individual only works on B&W and Muncie, most of his work is for race applictions and he has been around for years with an outstanding reputation -- it took me a month to get a appointment for service. This individual was a wealth on knowledge and was willing to share it. I mentioned to him that I use Mobil 1 gear lube in both the trans and the differential. He recommended that I DO NOT use synthetic lube in the trans or differential. He stated that both the trans and differential were disigned in the sixities with Dino gear lube in mind. In other words that were built to run/work the best on the regular gear lube. The posi diff has small clutches in there that reguire a certain amount of friction to perform properly as does the trans with the syncros. The synthetic gear lube will be to slippery for the posi clutches and the trans syncros to function as designed. With the Posi diff he said you may wind up with a single wheel drive because the clutches will not engage. Interesting isn't it. I decided to go with what he said. Dino gear lube for the trans and diff. Steve

 

[JohnZ]

All I've EVER used in all the T-10's, Muncies, and diffs in all my Corvettes, Z/28's, and project cars for the last umpteen years (and almost as many cars) is what they were designed for - brand-name 75W90 gear lube, plus GM Posi Additive in the diffs. Have never had any sort of problems or leaks, and see no reason to use anything else. Based on the mileage accumulation and moderate duty cycle our classics see, there's no economic or durability justification for expensive synthetic lubricants; I just use what the General designed them for, and have no problems or "mysteries" to solve.

 

[srthom13]

JohnZ, I too have finally come to that conclusion. No need to spend the extra dollars when the regular name brand Dino oils work just as well. thanks, Steve

 

[Gerry]

The only fluid I would use in the posi is the GM brand plus their additive and likewise GM for the trans, however I drive my car hard and fast often (17,000 miles last year) and the added protection I get in the event of catastophic failure (fan belt, water pump etc.) has made me a user of synthetic oil. I believe some new technology can be better for our older cars. Not dogma just my humble opinion.
I change oil filter every 2000-3000 miles, oil every 5000.

Best regards,
Gerry

 

[rowingone]

Yes I agree . . what damages a motor is not oil break down but rather the acids that accumulate in the oil as a byproduct of combustion . . the only way to remove them is to change the oil - if you go longer between changes but use more expensive oil . . I think you're actually doing more damage than if you used the standard oil and changed it more often.

 

[66427-450]

I switched from Mobil 1 to Shell Rotella T 15w40 for my '66, because;

- Based on my usage of the engine/car I change the the oil due to "contamination" before it "wears out" (oxidizes). So the sole benefit of synthetic is not relevant
- Additive package is very good. I’d bet that it provides as good, or better, wear resistance (than Mobil 1).

I don't start the car below 40 degrees, so 15-40 is fine