Is it safe to add 75w90 Gear oil to an engine ?

Status
Not open for further replies.
Joined
Sep 12, 2004
Messages
24,362
Location
Central Florida
I have a neighbor that added an entire quart of 75w90 Pennzoil Gearoil to his engine, cause he didn't want to throw away the unused gear oil.

If the sump is 5 quarts, will anything bad happen ?

I told him I had 190 quarts of oil in storage and offered to give him a quart of oil, but he said 75w90 would do just fine.
pat2.gif
 
If I were him I'd have just run 4 quarts of oil and given away the gear oil, then it would have worked out better for everybody.
 
Quote:


I have a neighbor that added an entire quart of 75w90 Pennzoil Gearoil to his engine, cause he didn't want to throw away the unused gear oil.




Your neighbor sounds like the kind of guy who went around sticking things up his nose and peeing in electrical outlets when he was a boy.
smirk.gif
 
No, It is not good. Gear lubes have a different PH then motor oil! It would be like adding a quart of vinager to your gallon of milk. It is going to cuase the milk to go bad and curtle in a hurry like was the TBN on his oil will be shot in a hurry. You also run into the problem that gear lube and it's VII's are not designed to work at the tempature that motr oil does and is also not designed to burn cleanly. It is preety easy way to stick up the rings.
 
(back in the day visions of The Old Ranger or 20 mule team Death Valley) 90wt hypoid would foam when mixed with motor oil. They may have changed a few things since the 70's with the stuff ..but there was no compatibility at one time. I mean beyond any insidious effects.
dunno.gif
 
I once put a litre of gear oil in my petrol tank to spread the evaporation points to the max...pinged like an busted arsehole until I added enough mothballs to get the octane back up.

I'd not run gear oils in the crankcase for all the reasons mentioned above.
 
offtopic.gif


"until I added enough mothballs to get the octane back up."
laugh.gif


Ha - I used to add Moth Balls to my gas in 1977 to get the octane up on my '68 GTO...
laugh.gif
 
I will talk to him later this week to see if the F-150 is smoking with the gear oil he added. He pulls a boat with this truck and he figured no harm would be done to an old engine.
 
Gear oil ? That's for wimps. I put a zerk fitting on the oil filler cap, and just touch up the grease until it oozes from the PCV fitting.

:^)
 
I had a 78 Ford Fiarmont when I started driving that used a qt of oil every 20 miles or so.After switching to the cheapest 85W150 gear oil I could find it used a quart about every 50 miles and lasted around 10k miles before developing a terrrible knock and I traded it in.
 
Quote:


I had a 78 Ford Fiarmont when I started driving that used a qt of oil every 20 miles or so.After switching to the cheapest 85W150 gear oil I could find it used a quart about every 50 miles and lasted around 10k miles before developing a terrrible knock and I traded it in.




So you could drive to the parts store, pick up a quart of oil/grease, drive home, and fill it. Check it the next morning & repeat. Sounds like the movie Groundhog Day.
 
Yeah the thing is is that it didnt smoke it leaked out that fast.I put 2 valve cover gaskets,1 rear main seal and 2 oil pan gaskets on it and couldnt stop the leak.I never pulled the engine but I think it might have had a big crack in the block or something
 
At work I had a Ford van that the oil pressure light would come on at idle so for 3 years I added 90 wt gear oil to the oil no problem.
 
I think 75/90 gear oil is approxamentally equal to a 40 wt oil at engine running temperature. I would suspect no harm if only done one or twice in the ratio stated.
 
Status
Not open for further replies.
Back
Top