18mpg. True or False

[will.mccay]

Hey everyone. This is my first post. Im picking up a 1986 k10 Monday. It is a 350tpi, 700r, 373 rear end with 35's. The guy im getting it from is pretty highly thought of in the area for the trucks he builds. He says he consistently gets 18mpg just driving around town. Im just wondering if that's a real possibility or maybe a bit of a stretch. Does anyone have any input?

[dvdswan]

my 1st thought is.... is the speedo correct?  99% of the time when intalling larger tires the owners don't do anything with the speedo so it will register miles less, then when it comes to calculating MPG the use the fudge factor to thier favor.

i.e. speedo says 60 mph when the truck is actually doing 66 mph.

[zieg85]

my 1st thought is.... is the speedo correct?  99% of the time when intalling larger tires the owners don't do anything with the speedo so it will register miles less, then when it comes to calculating MPG the use the fudge factor to thier favor.

i.e. speedo says 60 mph when the truck is actually doing 66 mph.

Then the mileage would be calculated lower... 18 seems to be in reach if it is driven with an egg between the foot and the go pedal if set up right.  Even with the 35's that trans with a 3.73 shouldn't struggle at all to get going.

[bake74]

     I agree with zeig, but being realistic if you bought the truck, could you drive it around all the time and never go over 25 mph ?
     Dvdswan has a valid point also, unless he has re-calibrated the transmission with the proper spedo correction attachment, the mph on the gauge will probably not match the actual mph.

[Irish_Alley]

tpi or tbi?
i dont see 18 in city. now once hes up to speed the 35s will act like a second od and the engine wont be working as hard to turn. but like dvd said. he may not have corrected his speedo and is adding more mileage than he should to try and calculate his mileage

[will.mccay]

Thanks for the input. I didn't think about the speedo being off. I'll check on that. It is tpi.

[VileZambonie]

He's lying but you don't drive one of these trucks if you're looking for fuel efficiency. You drive them because you love them.

[Captkaos]

Ditto.  He isn't getting that mileage something is off.  Either is speedo and/or gears.

Chris Lucas
73-87chevytrucks.com
captkaoscustoms.com
squarebody.biz

[will.mccay]

Well yeah I have a 350 with a 4 barrel edlebrock and I know how crappy the mpg is. My question is if with the right tuning on a tpi if that's even possible. Ill let y'all know here in a couple weeks what I really get.

[Irish_Alley]

I know with my 38s 4.10 sm465 and 350 I can get 9-10. But that's keeping her at 55 nothing over. So the od might help and 35s help and taller gears and the tpi I guess I could see 15 with that setup so maybe 18 Idk only time will tell and verify speed with your GPS

[Engineer]

Around town that is a 10~11 mpg truck at best.

14 highway. Maybe.

[ehjorten]

A 2013 4WD Silverado with a 5.3L is only getting an average of 17 (15 City/21 Hwy) on gasoline.  No way that '86 is doing that with 3.73:1 rear gears!

[greasemonkey54]

my 86 with 305/700 and 2.73 gear gets 16-18 mix of city/ highway, the more highway the better. around town where I live means traffic and if I do mostly city I get 10 or so