I bought a 91 EA82 with EFI and automatic for my wife and I'm only getting 22mpg.  The check engine light comes on after a few miles but runs fine.  This mpg seems low.  I had an 89 with carb and auto that got 28mpg.  I was expecting as good or better with the EFI.  Any ideas?

That check engine light is probably due to a bad egr solenoid, which is a common failure on these guys. Search the ultimate Subaru repair manual to find the guide that explains how to pull the codes and read them. If it's a faulty solenoid it can be replaced with any electrical vac solenoids.

How long since the last tune up. Spark plugs, wires, fuel filter, air filter - all can contribute.

 

Seafoam is great to find lost horsepower and improve MPG.

I have always had low 20s mpg with all of the 3AT wagons I've run. I am heavy on the throttle.

Put new plugs, wires, cap, rotor, filters and oil when I got it.  Also, the automatic was swapped out with the one from the 89 since the original was locked up.  It passed California smog with the check engine light.  The smog guy could not decode the light based on his data.  At first he said he could not pass because of the light but he got it to shut off for the start of the test and the readings were fine.  I was thinking that maybe there was some feedback to the EFI that was out of wack and that may be related to the check engine light? I'm sure Subaru (like every one else) changed to the EFI to pass the newer smog rules so maybe there is something amiss telling the EFI it needs more fuel than it really needs resulting in the poor mpg.The 22mpg is driving at 60mph.  My wife is not impressed since her big 97 4x4 Dodge diesel gets 22mpg.

 

What is Seafoam?

I average around 21 to 23 mpg and I run between 65 and 70 mph. Seafoam is a brand name of an additive that you add to your fuel or directly to your crankcase to clean the internals of your fuel system or your engine. I have never used it so I'm no expert but there are a lot of different opinions on the product when I read up on it.

Edited February 25, 201511 yr by loyale1993

22mpg on the highway sounds normal. My friend had a big diesel pickup. SiMilan numbers. But I spend so little on maintenance, taxes, insurance, car payments, that it is still cheaper per mile than anything newer that gets 40mpg.

22 in winter, near 25 in summer.

My old 89 with the automatic got 28, my 84 BRAT gets 32 and my old 84 GL got 30, so I was expecting something better with the EFI.  Maybe the old 89 car was the exception.  The truck only gets about 13mpg around town so the suby wins in that area, but I could still haul the suby plus another 2 tons of hay on the trailer and get 18mpg out of the truck on the highway. 

Egr solenoid. Almost guaranteed.

 

Also, anything that has a manual trans is going to do better than the automatic, regardless of fuel delivery. Your 89 auto must have been a unicorn, unless it has the rare 4eat trans. My 3 speed Loyale gets 25ish around town and the same on the highway. My 5 speed GL could do over 30mpg highway before the Weber.

I got a big boost in gas mileage,(4 mpg), after I replaced an oxygen sensor.  It was also the cause of intermittent check engine light,  but read the engine light code to be sure.

The O2 sensor can also fail in a way that does not trigger the CE light.  And fry the catalytic converter.  Yes, I learned this the hard way.

Egr solenoid. Almost guaranteed.

 

Also, anything that has a manual trans is going to do better than the automatic, regardless of fuel delivery. Your 89 auto must have been a unicorn, unless it has the rare 4eat trans. My 3 speed Loyale gets 25ish around town and the same on the highway. My 5 speed GL could do over 30mpg highway before the Weber.

 

True. I thought the egr was just a useless piece of emissions crap (and it is) but when I replaced mine on my FWD Manual Loyale sedan, my mileage jumped from 24 to 29. EGR recirculates unburned gases and therefore helps scavenge more mpg.

Edited February 26, 201511 yr by MR_Loyale