gas mileage help for 97 gtp

[TDWPgtp]

i have a 97 gtp and im getting about 18 mpg driving as fuel efficient as i possibly can. this means inconvieniently slow acceleration and timing lights to not have to stop, as well as other little things. basically if i were to drive the way most people do i would most likely be getting 15 mpg tops. can anyone help me as to the reason for this economy. thank you

[richtazz]

are you running premium as required, or trying to use regular gas?

[minidreams_n_scale]

Originally Posted by richtazz

are you running premium as required, or trying to use regular gas?

Hey Tazz ! You been a great help to me so far ! Answered all my question pretty fast ! So i trust you when you say WE MUST USE THE HIGHEST OCTAINE IN THE GT's OR JUST THE GTP's !

I hate paying 3 bucks a gal now ! LOL !

[BNaylor]

Welcome to AF.

Is that based on the DIC trip computer or manual calculations? Hopefully you have been resetting the DIC after every fillup. When was the last tune up? Air filter, fuel filter, spark plugs, etc. Any SES/CEL light or any other not-mentioned issues.

The premium fuel is for the GTP/GTX models with the L67 supercharged SII 3800 engine only. On the normally aspirated L36 SII 3800 regular unleaded.

[Burtnette]

Seems like everyone's gas milage dropped recently... think it has something to do with the additives they added to the gas for the winter? Like a bad reaction to our superchargers?

[TDWPgtp]

no, i have been using regular. how big of a difference will using premium make. and yes i reset the DIC mpg thing every fillup, and it is pretty accurate according to my calculations upon fillup. last tuneup was around this time last year. as far as i know everything that needed to be changed was, and i have not put on more than 6000 miles since we got the car.

also how do you remove the top half of the rear seat

thank you

[BNaylor]

Down here in West Texas the gasoline is oxygenated during the winter months. Also, it is normal in the winter to see a fuel economy loss due to longer engine warmup times and more time for the PCM module to switch between open and closed loop mode as a result. Best to see what the mileage is once winter is over and it warms up otherwise you could just be wasting time, effort and money.

Try bumping up to mid-grade unleaded with one range colder spark plugs.

[BNaylor]

Originally Posted by TDWPgtp

also how do you remove the top half of the rear seat

thank you

See link below for rear seat removal.

Click here

[richtazz]

Actually, here in Michigan, we get the better gas in the winter. We're forced to use the lower volatile summer gas here to reduce vapor emissions at fill-up. Mileage will drop in winter as bnaylor stated, it's just a matter of physics. Switching back to 91-93 octane could boost your mileage by 2-3 miles per gallon, plus it better for the longevity of your car. Too much pre-ignition from running a GTP on regular can cause piston failure. Again as bnaylor stated, GT's are happy with regular 87 octane, no advantage to running premium unless you're modded.

[BNaylor]

In most Western mountain states due to the altitude the octane level for regular unleaded is 86 which works fine on any GM car with the normally aspirated SII 3800. That is what I run in my wife's Buick Regal. In my Regal GS (L67) SII 3800 I switch between midgrade and premium depending on the cost. Also, I use one range colder NGK spark plugs in it. I have never seen any knock retard (KR) greater than 2 degrees at WOT. Under normal driving conditions KR is zero/nil. Confirmed by Autotap. No real hot rodding. Note: I have not tested using regular unleaded for obvious reasons. In my GTP I have to use a race gas (VP Racing) blend with 91 octane premium unleaded due to the 3.0" SC pulley and non-availability of any higher octane premium gas like 93 or higher but it is not my daily driver and I really don't care about fuel economy in it.