[THEFERMANATOR]

Originally Posted by spareparts

MJ, I was getting 14 out of my 02 Suburban when i first got it, I had been running 15w-40 in it. Some one told me to use 5w-30 like the manual said, i switched over and started getting 16 mpg on my next trip. I then switched over to Mobil 1 5w-30 synthetic and on our last trip to Florida, I averaged 18-19 on the highway running far faster than i care to admit

Your a LUCKY man Spare. 15/40 in an LS engine was putting you in DANGEROUS territory with oil pressure. I bet it was hitting 100+ on a cold start. The LS engines are designed to hold GOOD oil pressure on 5W30 oil. As for your check engine light MJ, there is a bulletin about the fuel tank purge valve assembly back by teh tank. It sticks alot and causes teh check engine light quite often. Next time it happens run by autozone and get teh code number and I can let you know if that is it. The GM part to fix it is less than $40 if it is the purge valve, but changing it is a pain as it is up by the rear axle underneath.