bluebonnet81 Posted May 20, 2012 Share Posted May 20, 2012 Is it typical that I only get 22-24 mpg in my 1981 GL hatchback 2WD 3 speed trans ? What can I do to improve this? The carb has been re built, new air filter, fuel filter, plugs & wires have been installed. A new cat was installed to pass CA smog, but there are some holes in the muffler. Does this affect mpg? Quote Link to comment Share on other sites More sharing options...
Gloyale Posted May 20, 2012 Share Posted May 20, 2012 That sounds pretty good to me. It would be better if it was not the automatic. Also if it wasn't 31 years old. Also, the new gasoline is terrible. EVERYBODY is getting worse gas milage. Buy premium, you'll get more MPG and power. Quote Link to comment Share on other sites More sharing options...
WoodsWagon Posted May 20, 2012 Share Posted May 20, 2012 It would be better if it was not the automatic. Buy premium, you'll get more MPG and power. Premium does nothing for MPG or power. It burns slower, so you may actually get less power. These older cars also won't advance the timing to take advantage of the higher knock threshold of premium, so you are literally pissing your money down the drain buying it. Unfortunately your MPG is limited by the 3spd auto. It has no overdrive and no lockup clutch on the torque converter, so a portion of the engines power is always being dumped into to the fluid as heat and the engine is screaming when you're on the highway. There's not much you can do but a 5spd swap. Quote Link to comment Share on other sites More sharing options...
Gloyale Posted May 20, 2012 Share Posted May 20, 2012 Premium does nothing for MPG or power. It burns slower, so you may actually get less power. These older cars also won't advance the timing to take advantage of the higher knock threshold of premium, so you are literally pissing your money down the drain buying it. Hmm.....I never urinate in my gas, or pour it down the drain? I put it straight in the tank and burn it. Perhaps that's why you don't get better MPG? Dilluting it and then pouring it out? Or am I mistaken on the definition of "literally". But seriously you're just wrong about premium gas. Burns cleaner....and I've measured the MPG differences. Noticable power differences. Additionally, the new premium has little and sometimes no Ethanol in it which also helps with MPGs, alot. Quote Link to comment Share on other sites More sharing options...
subaruguru Posted May 20, 2012 Share Posted May 20, 2012 You can talk to Bratsrus1 he did an impreza 1.8 swap into his hatch with a 3.7 5 speed out of an rx and gets 38.4 MPG. Just my two cents. Cheers R. Quote Link to comment Share on other sites More sharing options...
ferox Posted May 20, 2012 Share Posted May 20, 2012 Is it typical that I only get 22-24 mpg in my 1981 GL hatchback 2WD 3 speed trans ? What can I do to improve this? The carb has been re built, new air filter, fuel filter, plugs & wires have been installed. I drive an '81 4WD Hatch (w/ 290k) with Hitachi carb & 4MT trans., so it's similar weight-wise to your 2WD wagon. I get 25-29 mpg and up to 31 mpg if I really pay attention to my driving. As others have mentioned it probably has a lot to do with your auto trans. If you do some research on the D/R 5 spd swap you'll find that you will want to talk to Brastrus1 for his conversion kit. It's a worthy swap if you are mechanically inclined, otherwise you will probably have to get used to the 22-24 mpgs. An SPFI conversion would also be worthy, and can be done in California legally. Quote Link to comment Share on other sites More sharing options...
presslab Posted May 20, 2012 Share Posted May 20, 2012 Premium does nothing for MPG or power. It burns slower, so you may actually get less power. These older cars also won't advance the timing to take advantage of the higher knock threshold of premium, so you are literally pissing your money down the drain buying it. I agree with all that, don't run premium unless your engine needs it. If you want the carb cleaned, dump a bottle of Techron cleaner in your tank every oil change. Quote Link to comment Share on other sites More sharing options...
Gloyale Posted May 20, 2012 Share Posted May 20, 2012 These older cars also won't advance the timing to take advantage of the higher knock threshold of premium, You advance the timing to maximum when you tune-up. Also, again, simply for the less ethanol, you will get better MPG with premium. Quote Link to comment Share on other sites More sharing options...
natext6 Posted May 20, 2012 Share Posted May 20, 2012 I ran 94 through my 89 xt6 and got the best mileage I've ever noticed. Don't know if this applies tho:o Quote Link to comment Share on other sites More sharing options...
wentz912 Posted May 20, 2012 Share Posted May 20, 2012 I would think that the additional cost of the premium would be more than the offset in fuel economy that you see. I run 87 from Safeway in my wagon(22-28) and the truck(13-20), only the bike gets Premium wherever I stop. Quote Link to comment Share on other sites More sharing options...
Gloyale Posted May 20, 2012 Share Posted May 20, 2012 25 mpg vs. 22 = 13% increase in milage $4.40 Premium vs. $4.00 regular = 10% more cost. Slightly more cost effective, lot's better for the engine, fuel system, and driving experience. Quote Link to comment Share on other sites More sharing options...
ShawnW Posted May 20, 2012 Share Posted May 20, 2012 Did you do stock NGK plugs "vpower"? Those seem to do the best MPG of any I run in old Subarus. Quote Link to comment Share on other sites More sharing options...
bluebonnet81 Posted May 21, 2012 Author Share Posted May 21, 2012 I will look into the 5 speed trans option. I can tell that there is a lot of energy going into spinning the motor that fast ( about 4k @ 60 mph ). Where could I find a compatible 5 speed manual? Are there any other significant parts needed to switch it out? I will do some research, and talk to that Brast guy ... I will also compare a tank of premium gas to 87 octane. I dont remember which plugs I put in. It was whatever the cheaper ones were. Quote Link to comment Share on other sites More sharing options...
hatchsub Posted May 22, 2012 Share Posted May 22, 2012 I went from 24-25mpg highway to 30mpg highway when i did a 5 speed swap on my old sedan. As others have said double check all your ignition components and then if they all check out...i think its just that trans thats holding you back. The 3AT was terrible in both of my older subarus. If you like driving stick you will love a 2wd 5 speed trans. It really turns the car into something fun to drive. Quote Link to comment Share on other sites More sharing options...
sosubeme Posted May 22, 2012 Share Posted May 22, 2012 Do you have Ethanol-free gas locally available? Ranges from .10¢ to .15¢ more per gallon than the "blended" where I'm at. Get a mild bump in MPG for my '96 OB, also seems to run better / quieter. With 220K on the clock, I'm for any little bit that helps! Quote Link to comment Share on other sites More sharing options...
ferox Posted May 22, 2012 Share Posted May 22, 2012 Where could I find a compatible 5 speed manual? Are there any other significant parts needed to switch it out? I will do some research, and talk to that Brast guy ... I mistakenly pointed you toward a 4WD 5MT. You don't need the conversion kit for a 2WD 5MT. The 2WD manual transmissions are all 5 speeds, so all you need to find is a manual trans. for an ea81. The transmission cross member is probably different between the auto and 5MT and obviously the center console portion where the gear selector comes through the floor. You will probably have to figure out the correct wiring connections to things like the neutral safety switch and hook them up to the corresponding switches/sensors on the 5MT, but that should not be very difficult. You will also need the MT pedal assembly and bracketry for the clutch cable. All of these things should bolt in for the most part. Hopefully someone who has done the switch can chime in with more details. Quote Link to comment Share on other sites More sharing options...
hatchsub Posted May 22, 2012 Share Posted May 22, 2012 Things for 5 speed 2wd swap: Trans pedals crossmember radius rod plates (these are what the crossmember bolts to...they are different between autos and standards) flywheel full clutch kit shifter boot (lower) center console shifter clutch cable There is a bit of wiring to get the reverse lights to work so if you go through with this make sure to get that as well. It is not a hard swap at all. Everything is bolt in with no mods to the body of the car (unlike my camaro). Quote Link to comment Share on other sites More sharing options...
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