Mileage Decrease

**BluBurb89** · 07-26-2009, 12:20 PM

Hello,
I'm on a road trip from WA.St. in an stock '89 Silverado 'burb running a 350 TBI w/od that is well maintained. On the way down to AZ. I averaged 18/20 mpg using CC @ 57mph and running @ night. While in AZ my mileage dropped to about 13/15 using the same driving habits and I didn't do a lot of city driving.
I'm planning to relocate to the area and would like to know if anyone thinks that this problem is due to the heat in the area (the only thing I can think of) and if so what they've done or think I can do to remedy this.
I'm considering using a Hypertech chip upgrade along with a their 160 or 180 deg. thermostat and air filter housing modification and maybe a TBI riser.
Thanks for your input.
Ted

**retired2001** · 07-26-2009, 01:04 PM

It may be the heat, I've never seen that to be a problem when traveling through that area. I used to loose performance when I went "up" in elevation from down here in Texas going up to Colorado. There may some difference in the "blend" of gasoline from Wa. to Az. also, but I don't know. You were getting good mileage on the way down, though. Good luck!

**BluBurb89** · 07-26-2009, 02:43 PM

Thanks for the response. I always do well on mileage if I use the CC and OD and don't get above 60, but it sure seems to P.O. people. I get a lot of hand gestures, horns and lights! they don't seem to realize that it was built to function best at that speed. What degree thermostat are you using?

**vncj96** · 07-26-2009, 02:57 PM

your MPG will start to vary because of air when you go up in elevation, if your car isnt tuned for it.

**BluBurb89** · 07-26-2009, 03:09 PM

Please elaborate; are you talking advance, plugs, ECM settings.....

**BluBurb89** · 07-26-2009, 03:26 PM

When "retired 2001" mentioned "up" I didn't relate it to elevation above sea level. I related it to map location...Duhhhh. With Phoenix @ 1,117 ASL and Tucson @ 2.389 ASL: I think I might just be getting a clue. I'm real glad you guys don't mind sharing your expertise with the clueless like me.
Thanks Guys, Ted

**vncj96** · 07-26-2009, 03:32 PM

When it comes to tuning your vehicle for elevation changes I am not sure what you wold have to do, some will say the computer will adjust but with less oxygen all it will do is add more fuel this would create your loss for MPG

**retired2001** · 07-26-2009, 10:02 PM

Originally Posted by BluBurb89

Thanks for the response. I always do well on mileage if I use the CC and OD and don't get above 60, but it sure seems to P.O. people. I get a lot of hand gestures, horns and lights! they don't seem to realize that it was built to function best at that speed. What degree thermostat are you using?

I drive a 39' motor home with my Chevy on the back, so I can relate to "people being PO'd' because I drive @ 55mph ( best mileage) and legal limit in California. I just get there a little later!

**Crakums_GT** · 07-26-2009, 10:36 PM

Lol I lived in Tucson for 5 years. My truck ran better there than here in ND. Of course I took her out on more fun trips there too because there were so many places to go off roading. Here everything is owned by farmers or reservations so there are not many places to do that sort of thing. I think it has to do with your vehicle's attitude. If she's not happy there then she'll let you know lol.

-Greg