Man, I hate to even mention this. - F-Body Road Racing and Autocross Forums

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.

AndyJ View Member Profile	Aug 23 2006, 03:14 AM Post #1
Advanced Member Group: Advanced Members Posts: 997 Joined: 28-June 05 From: North Dallas, TX Member No.: 791	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.