[mcrews]

Recently (july 13-29) drove to Dallas from Sacramento and back. about 1750 miles each way. I dont travel 'light'. "Heck it's a 4 dr w/ a trunk.....why not fill it!!!" You get the picture.

I have had the sg for about a yr. It sits right in the middle of my gauges so it gives me instant info w/out looking elswhere.

The 02 Infiniti Q45 requires 91 octane. However, around town I didn't really care and ran 89 or 87. I tend to be a very 'mpg' kind of driver and didnt really notice a difference.

I hit the 'grapevine' (15 miles of climbing to get into the LA basin on I-5) at around 3:45 pm Temp was around 98 degrees. I had a tank of 87 octane.
The temp gauge on the SG got to 233`degrees. (I had installed a new themostat 180 degrees right before the trip. the car just hit 200k and I figured ....might as well) I started worrying because the car warning for OVERHEATING is triggered at 242.
I have driven the grapevine 8 or 9 times and never had an overheating problem before. The car also seemed to be 'slipping' or really trying to go faster.

Well as I was going down into the LA basin I hit rush hour and was stressing all the way for the next 2 hours. I stopped at a Pepboys and bought a 10 inch aux fan and a small trans cooler. Since i was headed into AZ and the high was 113 the day before I was really stressed!!!. I service the car very regularly and really try to pay attention to the little things.

Next morning I get gas, It was cheaper so I got the good stuff 91 octane. I still had not made the conection. As I was driving, though, I noticed the difference and started using IGN and LOAD along w/ TEMP on the sg. I got out the sg manual and read about IGN. Seem that the engine will advance or retard based on OCTANE and air Temp.

Sure enough, the IGN (TIMING) was running 29-36 and the temp never got over 207. On the next tank I ran 87 again but had picked up some OCTANE boost. THe IGN was at 21-27 and the temp was as high as 213.

WHAt did I learn: When traveling on the road alway run the best octane possible (they have 93 outside of CA!!!) WHen in town on short trips I can run midgrade everyother tank.

Other cars may be programed differently. I think there was a post that said octane did make any difference in mpg. But given that my car requires it, running anything less, especially under a load seems to make a difference in performance.