Good oil for 4.3l GM truck V6?

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This engine is basically the same design as the Chevy 350, with two cylinders lopped off. So it's easy on the oil somewhat.

Did you want to go with a fully synthetic or conventional oil? What type of drain intervals are you considering? What type of driving conditions, city, highway? How many miles are on the vehicle? We need all this info before making a proper judgement.
A good 40 weight oil such as GTX or GTX HM would be a good choice. M1 15w50 in the summer would probably work well too cause M1's viscosities are at the low end of the spetrum.

M1 SS 10w30 worked pretty good for me. My analysis is posted here.

Patman, you would think so, but judging by mine and dickwells analysis, this motor seems to thicken oil up pretty quickly for some reason.

I will be testing Red Line 10w30 next. It will be a while before analysis. But it will have about 15k on it
If the motor is going to see typical truck-type service that means lugging and high low-RPM loading (slow engine speed, more than typical weight in/on vehicle).

I think the key is the barrier additive package. I know I wouldn't use any older Mobil 1 Tri-Synthetic you might have laying around.
SuperSyn is greatly improved but it's a waste unless you are going to the 5,000 mark between oil & filter changes.

Schaeffer Supreme 7000 (synthetic blend) 10W30 or even 15W40 would be good choices. If you want something cheaper, go with Pennzoil Long Life 15W40 which has a similar amount of molybdenum (180ppm).

--- Bror Jace
Thanks for the advice.

The truck spends most of its time empty, cold starts are infrequent, and the use is more highway than city. It never gets below freezing or above 92F here.

Therefore, I'd probably do just fine with darn near anything for 5k intervals. I passed the 3k mark with Exxon Superflo 10W-30 and the oil looks so good that I've decided to keep going. I might drain and have it analyzed at 5k.

I do like the idea of a 15W-40 universal, since I can run it in the bikes as well. Maybe I'll give Pennzoil a go and see if all that moly makes my wet clutches go on strike.

The reason why I posted is because the psychological 3k barrier is a tough one to crack. I swear I hear the truck in my sleep, asking me to change its oil.

I've had excellent results with Mobil 1 10-30 in my 94 S-10 w/ a 4.3. To date the truck has 194K miles with no oil consumption. The truck has no oil leaks nor does it burn oil. I've used Mobil 1 and a good filter since I bought it new. I change oil at 10K intervals.

I live in houston so our climate is similiar, although it does get hot here. I drive mostly on the highway.

I'm confident the motor will last until 300K miles. To date, no unscheduled maintenance has been needed.
My '94 4.3 in a C1500 (purchased new) used more than a normal amount of oil on 10W-30 Valvoline. I started using straight 30 in the summer and drastically reduced oil consumption. Since I owned that truck, I have discovered 15W-40 Delo, which I would highly reccommend.
I run Amsoil 10w30 with a bypass filter and a much larger high flow filter. I also run Amsoil 80w90 in the rear and 75w90 in the front and transfer case. I also use Amsoils ATF in the tranny and power steering. I use to change out the full flow at 12.5k miles and drain and replace both filters at 25,000 but I think I will just analyse at the next interval before I change out just to see how it was doing. My truck is a Toyota 4x4 1992 with the 22RE 4 cylinder engine and automatic.
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