My tow vehicle is a 1996 GMC 2500 4x4 Suburban. I pulled an 18' open trailer until last October. It now pulls a 28' Pace enclosed. It is a 7.4l big block and has 293k miles on it. All original engine -- nothing has ever been replaced on the engine including all original water pump, PS pump, alternator etc. I have always run straight 30w oil and changed it every 3k. Since January, this truck has pulled a trailer 2x to California, Miami, Kansas, Louisiana, West Texas and Northern Nevada -- about 18k tow miles.

I used fleet oil analysis from Blackstone when I was in the trucking business and I believe in a good preventative program. The Suburban has been on regular analysis since it hit 200k. At 260k miles, it started to show up trace amounts of antifreeze which steadily increased over the next 2 tests. My best guess was a leaking intake manifold gasket.

At 260k miles , I started adding one quart of Lucas at every oil change. I also got some AutoRX and flushed the engine per their recommendations. This is not the first time I have used AutoRX. AutoRX was also added during each oil change.

The last oil analysis was for a 3k mile interval which was solely my latest trip to Nevada; pulling 8k lbs of trailer and car over the Rockies in 100 degree heat. Here is the note that came in today from Blackstone.

"ANDY: Another small improvement in the potassium and sodium levels in your Suburban. Good
news! We feel we can declare this engine trouble-free (at least as far as we can see). You're closing in
on 300,000 miles and we see no signs that this engine is slowing down, now that you're past the
antifreeze issue. Wear looks good as ever and all metals are properly balanced for this type of GM
engine. The viscosity looks more like a 15W/40--is it possible a different grade was put in, or added as
make-up oil? Otherwise engine heat may have caused the viscosity to rise."


Everyone has their own opinion of additives. I use them where indicated and not across the board in every engine I have. Of course, YMMV. I will continue to test this engine every other oil change and the Lucas and AutoRX will be a regualr addition as well.

"Man, I hate to even mention this."

Yeah, you messed up now. Talk good about a vehicle and they will beat you up. I see a waterpump, alternator and starter failure in your future. Maybe even a timing chain thrown in for good measure.

260k? Sounds like rebuild time, be glad you got that much out of it!

Julie,

I had a 97 Pontiac GTP that was my commuter car back in the day. It went 330k with no major problems -- still running when I sold it.

Wow almost 300K and havn't even needed a valve job? That's impressive Andy. How has the transmission held up? 4L80E right? My tow vehicle is at 175K and I would like to get another 4-5 years out of it. It's not showing any engine or trans problems, but I didn't think the trans could go that kind of distance without a rebuild.

Phil,

The valve covers have never been off. Yes, 4L80E with tow package. With the open trailer, I would run in OD loaded or empty with no problems. With the enclosed trailer, it is always 3rd gear. Just won't pull it out in OD. That old big block is perfect for this application -- just gotta keep it fed. Another plus is a new crate engine is VERY reasonable.

ANdy