wow.....all of you guys are getting so much better mileage than I am.... I have a question.... would having a blown head gasket have anything to do with bad mileage because I believe I have a BHG. Also I was wondering how much better mileage would I be getting if I changed my spark plugs. Thanks.

I believe that having a BHG would kill gas mileage as it would alter your compression.

If the spark plugs are really gunked up then it will make a difference. If they are only slightly worn you won't notice much by changing them.
You definently need to focus in on the BHG issue first though.

it's funny that you mention the BHG and mileage. When I had my BHG, I had it for a long time and didnt realise it. My mileage was pretty good, I was getting about 400-450kms a tank. Now with my fixed HG, I get about 350kms a tank...

Tank info
 

Before BHG, 17/24mpg (city/hwy). After BHG, 15/22mpg. ????

Tank holds 18 gallons, per manual.

Also, attempting to measure true fuel MPG must be done by topping up the tank, driving 100-200 miles, then top up again. Divide the # of gallons bought into the # of miles driven, = MPG.

I always fill my tank, as I don't like stopping to pump more than necessary. Use the trip odometer to measure the miles between fillups.

Also...a very important note/tip....don't let your tank get below 1/4 full. The crap floating around in there will plug up the screen easier, which can starve/lean the engine fuel needed. And....the pump is electric, and it sits in the liquid gasoline to keep it cool. Pumps burn out 2-3x faster when you always run close to empty.

Learn your car. When my gage reads just above 1/4, I used 10 gallons.

Damn good advise mrnickleye.

To clean that screen you speak of one would have to remove and take apart the gas tank?

Keeping the fuel system clean really helps
 

^^^ You need to pull the fuel pump. The filter/screen, is attached to the inlet side of pump. You must remove the gas tank to get at the pump. Its such a big job, that I would replace the pump while I was there.

My pump is original on my '89, and still working fine.

I recommend using an injector cleaner in the tank every 10 or so fill-ups. (6 months). Techron is one of the best YOU can buy (I get proffesional stuff for the shop). They sell it at walmart, and chevron gas stations. Its in the gas at chevron and texaco.

Thanks for info.

What is this proffesional injector cleaner you speak of?
What do you think about B12 Chemtool?

"400-450kms a tank. Now with my fixed HG, I get about 350kms a tank..."


that is 240-270 miles a tank, and then 210 miles a tank...and if the tank is really 18 gallons, that sucks ass. thats 13-15 and 11. something. My monte carlo which was a carbed 350 got better than that when i didnt race anyone.

yea i drive my car hard sometimes. no wonder i have so many problems haha.

the original MPG for the supra
MPG (highway)------23
MPG (combined)-----19

I while back, I converted all that into KM's, and if my calculations are right, i should be getting about 400kms per tank....I dont know if I am right...so I think I am in the normal range...My car is weird haha....before and after HG kms, lol.

Sounds like you're running on some very crappy fuel there - granted its cheaper - but what octane? I fill up with 95 octane and get 375miles on a tank with careful driving, or 99 octane and get an extra 20 miles or so out of it. This is the Research Octane Number, not the Engine Octane (which i think you use in the US)