25mpg 71 C10. Need Your Help!

[Hottrucks]

I throw this out there and you can flame if you want but here goes

I have a 472 caddy in my C 10 with a th 400...mileage with my foot out of it around town is 19 to 20..highway mileage sucks because of the RPM...rear gears are 3:73...so think about that.....good torque with the right gears will result in good mile but like was said before its has to be a complete set up...don't look for a big motor to get mpg if its twisted to tight or lugs all the time?

[slotdad]

what did you use for exhaust manifolds/headers? I have a caddy 500 begging to go into my 69 c-30

[weaintscared]

Well I just might get a few Mpg from what y'all are saying I'm going to run a BBC but I did buy a T56 6 speed to go behind it

look at my build & let me no what u think
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[67_C-30]

A 6.2 powered 1/2 ton will absolutely get 25 mpg or more with an OD trans. I had an '84 K10 with a 6.2/700R4/3.08's and it got around 27 on the highway. Now, I will say I'd recommend a lower rearend gear only because 4th was useless in town. I kept it in Drive in town and put it in OD on the highway. It would be worth a few mpg to have a peppier truck IMO.

You can put the 6.5TD on it and add about 70HP and around 150 ft lbs TQ but you will see a slight decrease in mileage (despite popular belief). I've seen pretty much no change with the Banks set-up. They claim a gain in mpg, but I haven't really seen it - But - I haven't seen a decrease like I have with 6.5TD set-up. The Banks set-up does have a very slight lag down low whereas the 6.5TD set-up pretty much has a instant power. The difference is that the Banks is non wastegated and the 6.5TD has a wastegate. The wastegate allows pretty much instant spool, but costs some mpg. The Banks set-up does make a little better mid to upper range power. Both really wake a 6.2 and still offer good ecomony.

[rob32472]

with price difference of the two fuels would it be more cost effective in the long run to go with an ls gas powered engine? The ease of installation alone is worth something... just my two cents

[67_C-30]

Originally Posted by rob32472

with price difference of the two fuels would it be more cost effective in the long run to go with an ls gas powered engine? The ease of installation alone is worth something... just my two cents

That's a good point and a valid question. The 6.2 is actually an easier swap than a LS engine, so that's not a factor, at least with the 6.2. Another factor is that low mileage military takeout 6.2's are available for $300 - $400, and the LS engines, electronics, electric fuel pump, etc. are significantly higher. It would take a lot of miles to "pay" for the LS set-up i would think. I get asked all the time how I am affording diesel in my Blazer, but the truth is even ith it being higher per gallon, I still cannot come close to it with a full size gas powered truck. I have my doubts that a LS powered 67-72 will get as many mpg as a 6.2 powered truck. I am basing that off the fact that LS powered newer trucks don't get near as good as 6.2 powered trucks from the early to mid 90's. The LS powered trucks are gonna be a lot more fun though!

[mrein3]

First of all, you aren't going to get close to 25 mpg around town. No way. If you can find one, the 84 K10 67_C-30 is talking about got up there in the 20s on the highway but I doubt it did that in town.

How many miles are you going to be driving around town per year?

I put together a quick spread sheet. I made some assumptions.

Assume you pay $3.65 for gas and $4.00 for diesel fuel.
Also assume you some how get 25 with a diesel verses the standard 13 for the average 350 powered, carburated truck.
In 12000 miles or one year that 25 mpg truck will save $1449.23 over the standard 350 gas powered vehicle.

Now back in the real world where you can expect to get 18 on a really good day in that diesel verses that 13 you can already get with a good tune up with what you got, you're only going to be saving $702.56 in fuel costs per year - provided you drive 12000 miles per year.

If you drive less, say 6000 miles per year you can cut those "savings" numbers in half. In other words you're talking a whole lot of pain, suffering, and money spent for little to no savings in fuel cost.

Plus if you go diesel you have to deal with gelling fuel, heaters, and all the other fun stuff that comes from driving a diesel in the winter.

If it were me I'd keep what you got running in top shape and just drive it.