|
|
|
|
| Author |
|
|
Registered
Join Date: Nov 2002
Location: Los Angeles
Posts: 729
|
Gas Mileage Inconsistency
My '87 is getting 330 miles before the low-reserve light goes on. Next tank is 360-375miles. They are all commute miles. Same location and driving pattern. I suspect it has something to do with DME. One time I unplugged with cruise control wire on the speedometer, the reserve light goes on at 290 miles. I put it back, I got 370 miles again. Any comment?
__________________
Caliber 1987 911 Cabriolet |
||
05-27-2005, 10:16 AM
|
|
|
Registered
Join Date: Apr 2001
Location: Linn County, Oregon
Posts: 48,518
|
I know nothing about '87's, but are you changing fuel brands?
__________________
"Now, to put a water-cooled engine in the rear and to have a radiator in the front, that's not very intelligent." -Ferry Porsche (PANO, Oct. '73) (I, Paul D. have loved this quote since 1973. It will remain as long as I post here.) |
||
|
05-27-2005, 11:35 AM
|
|
|
Unregistered
Join Date: Aug 2000
Location: a wretched hive of scum and villainy
Posts: 55,652
|
I wonder how accurate your fuel level guage and reserve light are, maybe that's where the inconsistancy is. Does it take the same amount of gallons to fill up each time? miles divided by gallons would verify.
Funny thing is, my car gets well over 20 mpg when i stay out of the boost, but less than 10 mpg when I am in the boost alot. I wonder why that is? 
|
||
|
05-27-2005, 12:36 PM
|
|
|
Registered
Join Date: Dec 1999
Location: Novato, CA
Posts: 4,740
|
It is quite possible that your mpgs may not be accurate since the 911 gas tank is not properly vented under the spare tire. There's a 2 gal bubble that does not fill with gas when you fill an empty tank.
So after driving around a few miles you might top it off and find it takes an extra gallon of gas even though you just filled it. The reason is, when you first filled your tank, the air pocket under the spare had air trapped inside. As soon as you start driving off, the void under the spare starts filling with fuel at every curve in the road, acceleration or braking causing an extra gallon or so of gas to replace the air trapped inside the spare tire bubble. One way to avoid this is to take your mpg readings with no less than 1/2 a tank of gas to avoid an air pocket from forming under the spare and making accurate calculations impossible. Better still, add a vent under the spare so your mpg calculations are accurate. An added benefit of venting under the spare is the fact that you will now have a 23 gal tank instead of 21.1. Cheers, Joe Last edited by stlrj; 05-30-2005 at 09:38 AM.. |
||
|
05-28-2005, 05:00 AM
|
|
