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Fuel Economy

xactorocker

New member
Joined
Jul 10, 2018
Location
Atlanta
Hey I'm getting around 11 miles per gallon, which from my knowledge is not great. So what I have done is change plugs wires and the o2 sensor. Also my ac does not work if that's any help. Idk if clutch is stuck if that could cause it. One more think I also dont drive more can 3 miles at a time just to work and back engine does not heat all the way up. Any help is appreciated thank you. And the car is a 85 245 with the m46 trans.
 
Spark plugs look good? tires inflated correctly and correct size? Car idle and run good? Still have catalytic converters? Was mileage higher last Summer? more info helps
 
Considering that it is Winter in Atlanta, even though it has been a mild one, and you only drive 3 miles per trip I would suggest that 11mpg is about what you should expect.

The tire pressure suggestion is a valid one. If you last tested the pressure last Summer they are probably reading 24psi now.

Do the spark plugs and that may add 1-2 mpg at best.

Take it on a road trip to the Georgia mountains, check the mpg and report back.
 
Thank you all for the help going to go check all these things out tomorrow. And I actually put in new spark plugs last week. And good idea for the mountains, I will go camping soon up there.
 
Even in fairly heavy (not yet Atlanta bad, but the infrastructure here is reaching bay-area/atlanta levels, soon to be Hell.A-Scape), an EFI 240, unless it's like -40 out, should get about 18ish city with typical driving habits.

So many variables for economy, but that's definitely below what the window sticker would suggest :lol:. 20ish city traffic mix-27highway is a healthy/average N/A EFI 240 in a moderate climate.

Even if it's pretty cold out, no block heat, it should get warm within 2 miles, 240s heat up fast with the heater valve closed if the T-stat is any good, even non-turbo models without a watercooled turbo to exchange lots of BTUs right next to the hot exhaust into the cooling circuit.

My extensive 3 seconds of googling suggest that March in atlanta should be 43-66ish degrees out/mild/moderate?

Even navigating stressful San Francisco hills/horrible traffic on terrible california gas with stuff on the roof, the beater '87 245 would get ~18-19ish. Coolant Warm-up should take 5?ish minutes of driving or ~1 mile cruising at 60mph steady in the flat with the heater valve closed on a 45(ish)? degree day?
 
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I'm with you KJets - hell, MINE gets 19/26 if you keep your foot out of it. Just trying to confirm he's got a number that was calculated properly. ODO's off and then we find out fuel use is estimated by looking at the fuel gauge...
 
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I'm getting 20 pure city, 28 pure highway. I was getting 23 pure highway before I had my injectors ultrasonic'd and flowmatched. I'd try getting those cleaned out and see if it doesn't help. After seeing the nasty crap that was in the pintle caps, you'll want to get them cleaned.

Either that or buy some cheap injectors from the FS and swap em in...
Ohm test wires, check plug electrode condition and gap, look for distributor & rotor carbon build up, all those factors can slowly drag down your mpg.
 
Kjets so it is very heavily stop and go. So maybe that's part of it. You said EFI but would this be different if it is MFI that's what my 85 is as far as I know thank you.
Then I'm pretty sure its accurate but will give it a check
 
Kjets so it is very heavily stop and go. So maybe that's part of it. You said EFI but would this be different if it is MFI that's what my 85 is as far as I know thank you.
Then I'm pretty sure its accurate but will give it a check

In 1985 240 turbo has MFI. N/a has EFI.
My 93 wagon with just around town driving gets about 20mpg.
 
Ok well thank you. Is there any way that the catalytic converter is bad and that's why I'm getting bad milage? Dont know how old it is. Thank you
 
Ok well thank you. Is there any way that the catalytic converter is bad and that's why I'm getting bad milage? Dont know how old it is. Thank you

If it's plugged/melted, it adds parasitic pumping loss as your engine has to force the exhaust out of a restrictive environment.

If the cat honeycombs are broken or shattered, it won't affect mpg, just emissions.

your cat should be bolt on, take it off, shine a flashlight in there and take a peek.

I'd definitely suspect injection system first though. Think about how long it's been since those injectors have been cleaned (if ever). Your O2 sensor might sense that you're running at stoich when in reality, a cylinder might be running rich, and another might be lean, etc. you want all your cylinders to have equal air and fuel input so that when your o2 sensor adjusts the mixture, it does so effectively for all cylinders.
 
If you do have a 240 turbo. The cat is very close to the engine and it's very common for those to clogup when they get old. My turbo had a clogged cat back when I bought it in 1995. Over the years though, I've experienced both types of converters failing in various ways clogging the exhaust flow.
On a 240 turbo there is a test port on the top of the downpipe. You can install a pressure gauge in the port. If I recall correctly there should be very little pressure generated. Something like 1.5psi. Any more than that it's affecting the exhaust flow.
 
I'm getting 20 pure city, 28 pure highway. I was getting 23 pure highway before I had my injectors ultrasonic'd and flowmatched. I'd try getting those cleaned out and see if it doesn't help. After seeing the nasty crap that was in the pintle caps, you'll want to get them cleaned.

Either that or buy some cheap injectors from the FS and swap em in...
Ohm test wires, check plug electrode condition and gap, look for distributor & rotor carbon build up, all those factors can slowly drag down your mpg.

about the same numbers i was getting with my 88. solid 28 mpg on the hwy
 
My 240 Turbo w. B19ET + M46 was heavy drinker, around 20 MPG, next car was 245 with B200F + M47 and it used something 28-29 MPG. Daily commuting stayed the same.

I was like "whathahek" when consuming first full tank. I was used to get max. 300 miles with full tank, and with 245 odemeter kept running on. Full tank lasted almost 450 miles.
 
These numbers just seem crazy I just don't understand what problem could be causing me to lose half the fuel economy. I am really hoping it's because of the stop and go the whole way everywhere we will see.
 
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