I am getting really horrible gas mileage on my '87 GXE auto tranny. I rarely get more than 250 miles to a tank and thats with all highway driving. I have already done all the obvious things: major tune up, plugs, plug wires, cap, and rotor, air filter. I also have all new tires and alignment. I have also changed the oxygen sensor. I am running out of things to check and don't know what else to do, any ideas? My pocket can't afford so many frequent trips to the gas pump, lol

 

have you checked the fuel filter? How heavy is the car? Do you have a trunk full of stuff you really dont need? How heavy are the rims on it? What octane gas do you use? Have you tried a fuel traetment?

 

Something that some members have had cause very bad gas mileage in the past is the Cylinder Head Temp sensor. Some people have had gas mileage as bad as 10 mpg when this sensor has failed. Have you noticed that you car is running rich? I assume you are calculating you mileage when you fill up (just want to make sure you gauge is not bad but you are actually calculating mileage)

 

Very good point. The computer figures it isn't warm enough, so it sucks more gas to warm up. But it never gets there so it perpetually sucks the gas down.

What kind of mileage is on the car?

Grab 2 cans of seafoam. Throw 1 can in the tank, put 1/2 can through the intake and 1/2 can in the crankcase for about 70 miles then change your oil. If it's an injector issue, the seafoam should clear it up. After the seafoam treatment, change your fuel filter.

If your not sure how to properly use the seafoam, just do a google search on it. It's good stuff.

I get about 350 miles per tank on my 88.

 

350 miles ....on a 88? wow, that's pretty good.

 

Well, I only have 63k on it. That's also highway miles doing between 60 and 65. If I were to do more city driving with it, I'd guess 320 a tank.

I learned the art of conservative driving when I had a Jeep. If I were to get on it less, I'd be willing to bet I could come close to 365 per tank.

 

What kind of O2 sensor did you get?
Was it OEM or aftermarket?

 

More information on the CHTS (Cylinder Head Temperature Sensor), it's sub-harness, and it's location on the VG:





You can get all the parts from Nissan for a reasonable price. It is not an easy part to get to. It's great to do during a timing belt change though. Here is a link to an "easy" method that you can attempt. It has worked for many, but I was frustrated with not being able to get the sensor as tight as I would have liked though it did work:

http://z31.com/repairs/chts.shtml

 

You do also have to be very particular with the 02 sensor because they had many different 02 sensors for these cars and the brainchildren at your local autoparts store could easily have given you the incorrect 02 sensor. Go Nissan and you can't go wrong.

 

thats about whaty i got on my 87 before i went turbo now i havent had a chance to drive like a grandma to figure out, im so in love with the boost lol!

 

Every engine has a "sweet spot". It's that rpm range where the engine is most efficient. On the vg, it seems to me to be around 3k, so that's where I "try" to stay when I'm accelerating. Accelerate too slowly, and you're actually using more gas, as the engine is actually working harder. I learned this when I had a Jeep, but it applies to just about everything.

But the thing is, everything on the engine has to be in proper working condition.

since my last fill-up, I've been real conservative when accelerating. So far, at 1/4 tank left, I've racked up 310 miles. That last 1/4 always seems to go fast, so I'm looking at 370 miles for this tank. That's about 26 mpg. That's real good, probably the most you can possibly get, unless you were to draft a large truck on a long trip.

Now, if I'm on it all the time, I'll only get 320ish out of a tank. But, everything on my engine is in new condition. When I hit 200k, I won't expect what I've been getting so far.

 

Switch out the 02 sensoer