Effect of gear oil viscosity on transmission efficiency (Metro owners take note)

[TOOSTUBBORN2FAIL]

Originally Posted by Christ

Yep, many manual transmissions call for ATF. I think most Ford transmissions actually call for it, but you can use engine oil as well.

many chrysler mtx's call for atf, but, and this is a big but, it is used to save money. The synchros will wear faster with it, and it will not shift as easy as the correct mopar fluid ($16 a quart) or mobil one 10w30 high mileage. Its very important to use mobil one 10w30 high mileage if you choose to use engine oil, especially in a neon, as the synchros are made of a material called fiberide, and according to oil analysis, only those 2 oils (the mopar stuff and mobil one stuff) have enough zdp to prevent premature wear to the synchros. Mobil one is 99% the same as the mopar stuff.

ive used both royal purple and penzoil synchromesh oils, and neither shifted as smooth as the correct mopar fluid or the mobil one oil

[Christ]

Cool. I'm not personally concerned about synchros, cuz I don't use the clutch anyway, but yeah.

[TOOSTUBBORN2FAIL]

ya, i dont use them much either, 90% of my driving is freeway, but just wanted to make sure i posted in case anyone switches to atf then has problems. Its not really a immediate thing, more like a if you plan on putting 300,000 miles on the transmission thing

regular 75-90 gear oil on the other hand can destroy neon synchros in 5000 miles tho, thanks valvoline oil changers

[bzipitidoo]

Been using ATF in a 1967 4 speed manual Ford for years now. Originally had some heavy oil, might have been as much as 140W. It was getting very hard to shift into 2nd gear. Used to be fine, but then the shift to 2nd became stiff when the car was cold. Got worse, so that 2nd was hard to shift into when warmed up, and almost impossible when cold. Was taking serious force on the gear shift to get it in 2nd.

We switched to ATF, and 2nd gear has been fine ever since. Not sure how many miles we have put on it since switching, but at least 20k.

One thing about differential oil: has to be specially formulated for hypoid gears. Lot of pressure on those. ATF won't cut it.

[stovie]

Does any1 know what the viscosity of lucas oil additive is because it says if u put all lucas in ur differential it will iliminate wear and if it's about a 65w when ur supposed to use 90w i'd say it's definently worth it????

[trooper Tdiesel]

this incorrect oil problem ive dealt with in Isuzu's too.


many fast lube places for some strange reason
have it in there computer that they take 80W-90 gear oil in the trans, when its really needs to be 5W-30 engine oil

in one to five years the bearings are shot

[Moriene]

The high viscosity ensures transfer of lubricant throughout the gear train. This is necessary since the devices needing this heavy oil do not have pumps for transferring the oil with only a portion of the lowermost gears bathed in an oil sump.

[mikeyjd]

Originally Posted by MetroMPG

The other thing to consider: GM syncromesh is "semi-synthetic" , if I recall. So its viscosity isn't as stable as temperatures change as a full synth. (Meaning greater efficiency hit for those who experience truly cold temperatures part of the year.)

I've got GM Synchromesh (full retail pop! ) in my car now, but am planning to go to a full synth of the same or lighter weight, soon.

Just trying to decide which, and then seeing if my choice is even available in my small city.

Any final conclusions on which gear oil to best maximize fe without risking damage?

[MetroMPG]

Nope. I ended up just staying with the GM Synchromesh oil.

[Sean.Heihn]

Originally Posted by stovie

Does any1 know what the viscosity of lucas oil additive is because it says if u put all lucas in ur differential it will iliminate wear and if it's about a 65w when ur supposed to use 90w i'd say it's definently worth it????

The original Lucas Oil Stabilizer is quite thick, well over 90 SAE weight, Lucas Synthetic Oil Stabilizer is thinner than the original but still thicker than 90 weight. I know because I've put both in manual transmissions that required 75w90 oil. But they're not really an oil, they're a slick sticky substance, I believe they coat the moving parts when added to oil. I put original into my Corolla, which required 5w30 engine and 75w90 gear, mixed with synthetic oil and I swear it made the car slower to start when cold in the winter (nothing serious, just a few more turns, still started reliably), but Lucas advises against using original in lighter oil. So with my Yaris I used the lighter synthetic, but used less than the 20% called for on the label, I think around 10% in the engine and 10-15% in the transmission and haven't noticed any problems, even in cold weather.

Racers and off-roaders seem to like Lucas Oil Stabilizer, but then again, they push engines and drivetrains to the max, unlike us daily drivers.

Also the fact the engine and gear oil use different weight scales makes sense. 75w90 gear oil seemed way thinner than what a 75w90 engine oil would be, but it's really the same weight as 10w40-50 engine oil. And about using thinner fluid than called for in a transmission seems like a bad idea, unless there's evidence to back up its use, like the Suzukis and Synchromesh. So, I'd say, unless there's a problem with your transmission and you think it might be too thick fluid, stick with the recommended weight. A new transmission, or a rebuild, costs a lot more than the few more miles you can squeeze out of a tank with lighter fluid. Damage or wear may not be apparent right away, it might take years and thousands of miles for problems to show up.