MPG's

[BigMike]

Just filled up after setting the timing to 10*. It's up to 11.2 from 9.8.

[BarnieTrk]

That's great to hear, BigMike!
11.2 mpg is an easy 14% improvement over the 9.8 mpg. Now was that with the 87 octane (regular grade) or with the 89 octane (mid-grade) fuel?

Assuming that was with the mid-grade fuel, I'm confident that the mid-grade fuel didn't cost 14% more than the regular grade fuel. So, in the end, you have reduced your overall fuel cost......and the added benefits are the facts that the,

Truck sure has more pep and isn't pinging.

....because your engine has more pep with the better fuel and bump in timing, it likely means you don't have to give it as much gas to get the same work out of it, thus, better mileage. Regarding the the preditination ("pinging"), it is well documented that such pinging is bad for your engine bearings, so by eliminating the pinging, you're extending the engine life - also a good thing. This is all a result of your 'tuning' work! Congratulations, BigMike - Good Job!
BarnieTrk

[BigMike]

That's great to hear, BigMike!
11.2 mpg is an easy 14% improvement over the 9.8 mpg. Now was that with the 87 octane (regular grade) or with the 89 octane (mid-grade) fuel?

Assuming that was with the mid-grade fuel, I'm confident that the mid-grade fuel didn't cost 14% more than the regular grade fuel. So, in the end, you have reduced your overall fuel cost......and the added benefits are the facts that the,

Truck sure has more pep and isn't pinging.

....because your engine has more pep with the better fuel and bump in timing, it likely means you don't have to give it as much gas to get the same work out of it, thus, better mileage. Regarding the the preditination ("pinging"), it is well documented that such pinging is bad for your engine bearings, so by eliminating the pinging, you're extending the engine life - also a good thing. This is all a result of your 'tuning' work! Congratulations, BigMike - Good Job!
BarnieTrk

Thanks! This is with 87 octane.

[BarnieTrk]

Thanks! This is with 87 octane.

WOW - that IS impressive!

BigMike, Are you still thinking about trying a tankful or two of mid-grade fuel?

BarnieTrk

[BigMike]

Thanks! This is with 87 octane.

WOW - that IS impressive!

BigMike, Are you still thinking about trying a tankful or two of mid-grade fuel?

BarnieTrk

Yes, but I filled it again with 87. The next tank I'll do 89.

[fire truck]

I used to average 11-14 in the farm truck, I drive 80-90 for the first 10 miles in the morning....it was an auto, had a 2 something rear....

[BarnieTrk]

Yes, but I filled it again with 87. The next tank I'll do 89.

BigMike,
Cool,,, keep us posted on your progress!

By the way -- I suspect you likely have already done it, but for the sake of "just covering the base", how much air pressure do you keep in your tires?
Are you running 4 or 6-ply tires?
Either way, I'd suggest you run on the high side of the reccommended operating pressure (40-ish?).

I see so many vehicles driving around with half-flat tires, and I suspect those drivers would like better fuel mileage - but they don't take the time to check on their tire pressures often enough. And running on half-flat tires definitely eats into their mileage rate.

BarnieTrk

[matt2491]

I get an honest 15-16 mpg with my 292. But I am running 3.00 rear gears... and drive like a grandma 90% of the time... and am very conscious about fuel mileage. You could call me a hypermiler I guess.

[BigMike]

Update - the last tank of 87 I got 12.2 but there was a lot of highway driving.

I just filled it with 89 octane and will report back in a few weeks.

[BarnieTrk]

Big Mike,

11.2 mpg, and up to 12.2 mpg with a higher % of highway driving on 87 octane (regular grade) fuel - COOL!

What do you keep your tire pressure at?

While you're running the 89 octane (mid-grade gasoline), try to notice if you can tell a difference in performance, spark knock, etc. You may even be able to drive the same speed with less throttle. You also may be able to bump the 10* timing advance up another degree or two with the higher octane fuel....which may assist in even MORE mileage and performance!

BarnieTrk

[BarnieTrk]

Update - the last tank of 87 I got 12.2 but there was a lot of highway driving.

I just filled it with 89 octane and will report back in a few weeks.

Big Mike,

How is your mileage been?

BarnieTrk

[BigMike]

Update - the last tank of 87 I got 12.2 but there was a lot of highway driving.

I just filled it with 89 octane and will report back in a few weeks.

Big Mike,

How is your mileage been?

BarnieTrk

9.8 and 10.4 but my foot has been in it.

[Astrowing]

I got a little over 15 mpg in my '61 with the 223 a few months ago on a 150 mile trip. I kept the speed down to 60-65 mph.

[BarnieTrk]

Update - the last tank of 87 I got 12.2 but there was a lot of highway driving.

I just filled it with 89 octane and will report back in a few weeks.

Big Mike,

How is your mileage been?

BarnieTrk

9.8 and 10.4 but my foot has been in it.

HaHaHa!!!!!!!!!!!

[BigMike]

I've been driving the Slick to work a couple of days a week. Filled up this morning and mileage was 10.86.

Really need to think about getting rid of that 4.10.

[charliemccraney]

I doubt you'll see much change for city mileage with a gear change. I can actually see the city mileage dropping if you went too tall since it's more stop and go and you'll be working the engine harder for the go part. Highway mileage should improve, though.

Do you have a 9"? I'm actually trying to find a 4.11ish ratio in the pull-a-parts for my truck. They don't seem to be very common. So if you have a 9", I'd take that off your hands if you do swap to a taller ratio.

[BigMike]

I doubt you'll see much change for city mileage with a gear change. I can actually see the city mileage dropping if you went too tall since it's more stop and go and you'll be working the engine harder for the go part. Highway mileage should improve, though.

Do you have a 9"? I'm actually trying to find a 4.11ish ratio in the pull-a-parts for my truck. They don't seem to be very common. So if you have a 9", I'd take that off your hands if you do swap to a taller ratio.

Dana 60 8 lug

[BarnieTrk]

I've been driving the Slick to work a couple of days a week. Filled up this morning and mileage was 10.86. Really need to think about getting rid of that 4.10.

If I recall correctly, the numerically lowest gear set available for a DANA 60 is a 3.54:1. Even if you were to go down to the 3.54:1 gear set, the change would not be cheap and I doubt it would provide you with the 14-15 mpg results you desire.

If you gave yourself an extra 10 minutes to get to where you need to go every time you get behind the wheel - then drive 55-60mph - I'd bet your mileage would come up.

Bottomline:
I'd suggest you do the math as to how many miles you WILL drive your Slick a year and how much fuel (@ 10mpg) it will take to travel that far. Also be realistic with yourself as to how many years you will drive your Slick that far every year. Then determine how much a gear change will cost you. How much will you save in fuel costs with the gear change? I don't know where to find that answer........ Lastly, with those costs in front of you, determine what is best for your situation........
Good Luck!
BarnieTrk

[BigMike]

I hear what you're saying. A gear change would run me $500. I figure the C6 I'm planning will cost me around $1200 to install.

Once the truck gets A/C, I'll probably drive it to work every day. Commute is 42 miles round trip which is about 4 gallons of gas. If I could somehow raise the mpg's to 18mpg on the highway, I would save almost $30 a week based on $3.50 a gallon (safe side of prices), that is almost $1500 a year savings.

Now, what could get the truck to 18mpg? 302 or 351 with an AOD? Gears at 3.54? What's the cost? Would I sell the 352/NP to help fund it or keep it for originality?

It would be an interesting project.

This truck isn't going to be a tow vehicle so I'm not worried about capacity. It's just something to drive and maybe haul some stuff like lumber, mulch, etc for house projects.

[charliemccraney]

A roller cam, fuel injected 302 might touch 18mpg in a slick. If it's not one of those, don't waste your time on a 302. Going with an auto will make it more difficult.

I think it can be done but it will probably take several years to break even. And since there is not a known recipe for an 18mpg slick, you'll be on your own to figure it out which means you'd probably spend a good bit of money to make it happen. I'd start with the 352 since it's what you have. They don't have any compression. Give it some compression. Make it require mid grade at the minimum. The increase in efficiency should offset the increase in the cost of the fuel and result in increased mileage. I wouldn't expect that alone to get you to 18mpg but it will be a start.

I'm at about 16.5 right now with a 3.70, T5 and 292. I'm hoping for 18-20 when all is said and done. It's not really a goal. It's just that everything I've done to enhance performance seems to have also increased the mileage and I still have several upgrades to go before it reaches my performance goal.