Author Topic: 10W30 or 10W40? (Read 7408 times)

TRAN5AM · « **on:** June 07, 2006, 08:38:09 PM »

I am picking up my 78 from out of state tomorrow, and driving it back home. Since I have no idea when the oil was last changed, I am going to make a stop first to have it done, before hitting the road. What weight oil should I have put in?

ta78w72 · « **Reply #1 on:** June 07, 2006, 08:55:22 PM »

I've always used 10w40. But I'm in a very nice climate.

hesster · « **Reply #2 on:** June 08, 2006, 07:01:35 AM »

10W40 for all around and summer.
10W30 is OK also.
Staay away from Racing oils - 20W50 etc. unless you are racing.
I only use synthetic oil, as regular oil can not compare to it.
The concern about switching to synthetic and mixing oils is a bunch of crap. At GM, we only use synthetic on all of our high performance engines - Vettes and all of the V-Performance series (CTS/STS-V). These engines use 5W-30 only because they have very tight clearances to address fuel consumption and efficiency. Older engines like ours need heaver weight like a 10W series.

ta78w72 · « **Reply #3 on:** June 08, 2006, 08:27:28 AM »

I haven't switched to synthetic because the feedback I've gotten is that older cars will leak. I switched to synthetic in my T-10 transmission after I had it rebuilt.

I was thinking about switching to synthetic in my 99 T/A with the LS1 engine. But so far I've stuck with regular and change often.

So, hester, what kind of cars are you using synthetic in?

evilways · « **Reply #4 on:** June 08, 2006, 08:37:53 AM »

As far as putting synthetic in an LS-1 or -6, go for it, thin viscosity if your climate allows for it. I dyno'd 4 extra rear wheel horses using Royal Purple in my supercharged 2000 TA, granted , I'm not sure how much it would've gained stock, but this car was completely tuned to the max and still gained a bit with the oil.Went from 543.7 RWHP to 547.4 RWHP and gained about a ft lb of torque.It makes for an expensive oil change, but for $$$ to HP ratio, not too bad. PS...I miss that car, sold it in Jan...fastest thing I've ever touched...

ta78w72 · « **Reply #5 on:** June 08, 2006, 09:14:05 AM »

I've also been told that the weak link in the 98-02 T/A's is the rear end. And if you push the HP in the LS1 you're apt to blow the rear end. I thought I was doing great with the original 320 HP set up! But over 500 HP! Wow!!!

evilways · « **Reply #6 on:** June 08, 2006, 10:08:25 AM »

read: Moser 12 bolt rear, 3.73's,girdle....lol....yes, all that hp and an auto tranny...4l60e, rebuilt 3 times before I got wise and got a Rossler trans prof. built. It ran low 11's on street tires(ususally 1.9-2.1 60ft times...lots of tire loss :twisted: , never got to run slicks, but the est . was low to mid 10's .Did that G-meter thingy that plugs into the cig lighter, pulled .98 and 1.02 g's , 0-60 in 3.4. Never found out a top speed,but had fun trying.