I own a 1994 850 Turbo with 149,000 miles. I've had her since February of this year, and the dash always said my mpg was 20.2. Recently, it's decreased to 18.6 mpg. It's been a slow decrease over the past 3 weeks or so. What should I check/change/replace? If you could give me tips on how to check things out myself at home this would be greatly appreciated!

 

have you performed a tuneup lately if l may ask?spark plugs and wires? distributor cap and rotor?when was the last time you changed or checked your air filter? have ever runed a fuel injector cleaner through your gas tank lately?

from my experience, l have the same digital reading on my 1997 850R and mine reads 22.2 now. from the user manual l searched online it says the reading tells you the average miles per gallon you are getting but l dont think it is the actual mileage reading. l have studied mine closely, l get 22 miles to a gallon city wise and 28 to 30 miles to a gallon highway.l might be wrong but l have really taken a close look at it.
this is what l did.
1.l runed seafoam through the intake to clean the pistons and my valves
2. seafoam in the gas tank to clean fuel injectors and remove carbon from the tank,
3. l did a complete tune up.changed my air filter to K&N.
4.cleaned my MAF sensor

make sure you have the tires inflated to the manufactures recommendations. l get almost 30 miles to a gallon on the highway and 20 to 22 citywise

 

What he said

 

Maybe leaky injector(s)?

 

unload your trunk.LOL.l have seen alot of people with lots of gabage in their trunk and puts weight on the car.the car is already heavy and adding additional load will decrease miles per gallon

 

After you do what Slim suggests, read the FUEL MILEAGE sticky thread. It has lots of tips in it. I usually got 23/29 but mine has recently dropped to 19/24. I have a problem with my cluster that caused my drop but I'm about to fix that in the next few days.

 

RSPI do you drive a manual or auto transmission?

 

I have not done a tune up recently, no. My air filter is good, and I've used a fuel injector cleaner within the past couple months. But I haven't done the spark plugs, etc.

But the mileage just keeps decreasing every day, I'm down to 17.3 now!

 

I'm at 17.3 now also. I have an auto trans.

I think my injectors are leaking. When I start it in the morning the rpm's jump to 2,000 and stay there for about 3 seconds before it slowly falls to 850.

Which injectors are best for the '95 turbo's?

 

will a leaking injectors cause the rpms to rise that high?mine does the same.

 

doing a tune up might help.you know what l did?l runed lucas fuel injector cleaner on my first fill up, because l read it lubricates the pistons and cleans the valves. on my next fill l runed 1/4 of seafoam in my gas tank to help remove carbon from the gas tank and help clean the injectors. our 850 takes 18 gallons to fill up l believe, l wanted to run a test in my fuel economy and only got 6 gallons of gas. l made a 30miles high way trip back and fourth for four days and still had gas in it on the fifth day. l am probably getting 28-30 high way driving.do a tune up and do what l did and see there is any improvement.

 

The engine should normally start with a high idle and come down fast or slow depending on it's temperature.

A leaking injector will usually load the engine and not cause an increase in RPMs. A vacuum leak or a sticky Idle Air Control motor will cause the increased RPMs. If it's a vac leak it's the IAC that is jumping in to bring the RPMs back down.

 

Are you actually doing the math for each tank of gas or are you just relaying on the trip info unit to tell you ??

If you aren't doing the math then it's possible there is something in that info pad that's giving you false info.

 

thats true.he has to do the math.sometimes that reader can give wrong info till you reset.l reset it most of the time

 

@ Kiss: Thanks. I was starting to wonder and was thinking about changing my injectors.

@ Slim: I really don't think you read that Lucas lubricates the pistons, that's what your motor oil does. The Lucas is suppose to lubricate your fuel pump & injectors, clean the valves & injectors.
As for carbon in the fuel tank, I don't think so. The inside of your fuel tank will be as clean as a whistle. There may be a little grime in there floaing around that the sock makes sure doesn't get sucked up into the pump but other than that, the tank should be clean from the gas. Now the Seafoam will get carbon from inside the motor, like off the top of the pistons and off the valves & other passages. That's why I'm a little afraid to use it. Afraid that a small piece of carbon will get stuck in the edge of one of my valves and cause the valve not to seat on the head properly. A leaking valve (one that doesn't seat properly) will cause it to burn and crack.

I'll change the plugs in about 7k, they may be due a change now. I thing they were last changed at about 185k and I now have 213k. I purchased the car with 189k in 5/11. The plug wires are dated around 8/10 and I know the car sat for about 6 months before I purchased it so I'm really guessing on the age of the plugs. Heck, maybe I'll order some plugs today and get the car on it's original new schedule, that would have called for a set of plugs at 210,000.

 

thanks brother for the correction. l think l read on the lucas bottle that it lubricates the pistons.l think l misread it.

 

Oh, yea... The best way to check your fuel mileage is to use the fill up and do the math method. I do that about once every 3 months. But to be honest with you guys the built in trip computer is usually within 5% of the true numbers. If I'm getting 22 mpg around town, the trip may say 21. In all of my 850's it seems to error a little towards the low side but I'd rather that than the high.

Also, I tested it on running out of gas once in my yellow sedan. (KIDS, DON'T TRY THIS AT HOME. RUNNING YOUR CAR OUT OF GAS WILL LIKELY DAMAGE THE FUEL PUMP). I got a gas can and put it in the car when I got low on gas, then I drove around until the car started to run out of gas. About a mile after the dash showed 5 miles remaining on it the car started to run out. So I pulled over and put the gas in it.

 

running out of gas will likely mess up your fuel pump for real?l didnt know that.LOL

 

Mine also does the same thing.

 

Well, there is no mystery, here's the link:
Lucas Fuel Treatment : Lucas Oil= - Lucas Fuel Treatment