Oil Recommendation

[RICKDIZZLE]

Evening everyone...I have an 85 Cutlass with a V6 3.8 all stock motor. Has 132xxx miles on it. Have an ever so slight rear main seal leak. It's oil change time and wanted to see what the best oil is to run in these older motors? Any special type of oil I should be looking to run? Any special additives like Lucas or anything? Also how many quarts for this motor? Thx u everyone!

 

[86 regal]

I run a amsoil in everything, started with my bikes and really liked it so it's just what I put in everything now.

 

[MrSony]

All based on personal prefference. Yes, some oils are made differently or more cheaply than others, so at minimal stick with name brand if you can. I think at least in my owners manual for my regal with the 3.8 was 5w30. Oil has come a long way, so you could use 10w30 and be fine. I prefer valvoline, but that's just me.

 

[pencero]

A 3.8 should be happy with anything pure oil or blend, not full synthetic but don't use penzoil it smokes / burns o rings and 5w30 is too thin if its already leaking, also use any additive that has +zinc / ZDDP STP is ok but lucas oil is probably better but you get what you pay for. I like AMS oil but its kind of expensive for a 3.8L v6. That's like giving a starving child a piece of cheesecake...

 

[RICKDIZZLE]

Thanks for the replies. Lil confused...as I hear not to use synthetic, which I don't wanna use anyhow, but I thought amsoil was synthetic. I'm thinking of using Valvoline with some Lucas additive. What weight should I use w that slight rear main leak? Also how many total quarts for the 3.8...looking to buy what I need. Thx guys!

 

[Clarmo]

Be careful with fancy oils, perf. oils, and additives. If it still has a catalytic converter on the car, call the manufacturers first. Cats don't like some of that stuff. A buddy of mine toasted all 4 cats off his Ford by with fancy perf. oil. A GM might not be that sensitive 😉 but I'd make a call first.

 

[RunAwayNJ]

Usually use Quaker State or Valvoline oils in all my cars. The Olds 307 gets 10w30. I also always put in Lucas oil additive with every oil change for every car/truck we have. The Olds has 176k our Suburban 184k, and a Plymouth minivan with 118k all running perfect.

 

[axisg]

Nowadays the zddp is in short supply in motor oil. I know as I wiped out 2 lobes by using the wrong oil that I thought were supposed to be good for my flat tappet camshaft. On your 3.8 which is flat tappet as well you may need to step up to an Amsoil, Brad Penn, ect.. Even though they are synthetic, they have the zddp additive that is beneficial to keeping that 3.8 alive. If you run synthetic then bump up the thickness to a 15/50 or 20/50 to keep it from leaking past the seals

 

[RICKDIZZLE]

So what are the pros/cons of going synthetic? I have been advised by many people not to go synthetic as it "can cause problems" but no one has ever elaborated on such problems.

 

[Evan11]

10w30 or 10w40 high mileage oil (pennzoil, valvoline, or Castrol) is what I'd run, it has additives to help with small leaks.