City/Highway Mileage Differences

[crawdad]

When I picked up my new 86 a few weeks ago, I was pleasantly surprised at the mileage I got on the way home. The trip was mostly interstate driving and I was getting right at 18 MPG. I've just checked my mileage again which was mostly around town driving and I was amazed at the difference, only 9 MPG! I know there should be a difference, but I never would have thought there would have been such a huge difference. Anybody else with similar numbers.

[mySAVIOReigns]

Yea, I got 15 and 8, so a little less of a difference. My goal with my truck is to get at least 15 city

[piecesparts]

I get around 15 MPG on the highway and a mixed mileage of 13 (city and highway). When I run around a city a lot, then it drops to 11 MPG. This is all on a 383 stroker and a 700R4 tranny (with a 2400 stall converter--not a lockup converter) and 3,73 gears. I never have gotten really bad mileage with m y truck, in the 15 years that I haveowned it and the change in m otors has not affected it alll that much.

[f.monroe]

I think that a lot of these trucks came with 2.56 or 2.73 rear axles andthey are good on the highway but lug these trucks in town . A little lower ratio would probably bring up the in town mileage but will lower the highway mileage . Frank

[piecesparts]

My son's truck originally came with a 305, 350C tranny, and 3.08 gears. We changed it over to a 350 engine and then the tranny needed to be upgraded, so we went to a 700 R4, this killed the mileage with the 3.08 gears. We then p ut a 12 bolt posi unit under the truck and changed to the 3.73 gears, this gained BACK 2 MPG and now the truck gets around 14 MPG in mixed driving. The truck no longer drags down the road, the cruise control works good and it drives really well in the city. The motor runs at 2500 RPM at 70 MPH and seems to have plenty of power.

[crawdad]

I hadn't thought about the gears killing the mileage, but its got 2.73 gears in it, so I imagine that is the culprit. I've got an old 12 bolt rear end that came out of a 72 cheby. Does anyone know if that would bolt right in, or would I have to relocate the spring perches? I might just rebuild that with a lower set of gears. What do you think?

[Prerunner1982]

My 82 was that way mostly due to the large tires.. worked great on the highway, it had the same effect as an overdrive as far as lowering the rpm.. but the same tires had an adverse effect on my city driving as it too soooo much to get the beast rolling.. of course this was with 32" tires and 3.08 gears..

My 87 does much better and get about 16mpg in the city, unsure as to the highway done drive it on the highway enough to really get a good reading. The 87 is 305/700r4/with 235/75/r15s.. I believe the gear ratio to be 3.08 but have not really tried to figure it out.

[7387chevys]

Who has the 383 that gets 21/8ish they have a blue 76ish pickup as avitar

[piecesparts]

I have a 383, but I don't get any numbers like that. I would like to, but then I would have to give up performance for mileage. I just can't make myself do that. There would be no use in building a 383, if you are going to cut it's cojones off and make it a paltry mileage machine. Run what you brung--build it to go home at the end of the race.

[magnethead]

don't even ask what I get. 9 city and 10 highway, with 8.5 towing highway.

454-TH400-4.10's