Best MPG engine Size and setup

[Stewart G Griffin]

Actually, scratch all the stuff i listed for now.

 i think it would be best to do the cheap/easy stuff first in order:

1) Since you do alot of driving, i think using this guide and trying to find stations that only sell 100% gas is a good start:
http://pure-gas.org/

2) Focus on saving on gas first, then improving mpg;  So i would first look into credit cards that offer some sort of rebate on gas.  Exxon had one that rebated .15 per gallon off sign price.  This just ended this past october, but now they are offering a card that rebates .06 cents per gallon.  There are credit cards that offer 5% rebate at any gas station.  At current prices this is about .15 off per gallon.

[gto109]

Jason S will your set up run on natural gas as well?  With me living in central pa where they are doing a lot of gas drilling right now they are starting to put up natral gas stations around here.

[Jason S]

Jason S will your set up run on natural gas as well?  With me living in central pa where they are doing a lot of gas drilling right now they are starting to put up natral gas stations around here.

   
Some of the parts will work with a Compressed Natural Gas (CNG) setup, but overall no.  CNG is usually at 2,000 to 3,000 psi, whereas Propane (actually LPG) is under 200 psi.  Tanks, lines and regulator would be different. 

[gto109]

ok thank you I am just starting to think about doing this with my chevy and dodge.

[gildardo01]

Jason S will your set up run on natural gas as well?  With me living in central pa where they are doing a lot of gas drilling right now they are starting to put up natral gas stations around here.

   
Some of the parts will work with a Compressed Natural Gas (CNG) setup, but overall no.  CNG is usually at 2,000 to 3,000 psi, whereas Propane (actually LPG) is under 200 psi.  Tanks, lines and regulator would be different. 

i had no idea you needed such a pressure for natural gas... the tank to store natural gas must be extremely heavy do to the thickness of the metal to hold that pressure... kinda like an acetylene tank... sounds a little dangerous for it to be mounted in a vehicle

[Jason S]

I didn't want my posting on LPG to defer anymore from the overall question 78Chevyrado wanted to have answered so I started a thread on Alternative Fuels here http://forum.73-87chevytrucks.com/smforum/index.php/topic,25394.0.html in case there are any questions about LPG and/or CNG that I or others may be able to answer.

[78 Chevyrado]

As far as propane tanks go....  Their not common enough around here to be cost effective...  Around here its gasoline of diesel, even E-85 is hard to come by....  Propane would cost me about what it would to get a tank for the grille, which is too much.   

I'm just wanting which will be the best mpg setup.  I know 6.2lD is it, but i drive 60-65mph regularly, though i was in a hurry the other day and ran 80mph to get there quick....  i dont like going that fast on NON-OD.  But it was that or lose $450  Thats the kinda thing I have to deal with....  Yes I got $450, but whens the 350/TH400 gona leave me stranded...  I know it will,  its a mathematical reality, as I got the truck with 84K on it, it now had 144K on it, but what do I do when it happens...lol

[78 Chevyrado]

For when it does quit...  I got a lil taste the other day...  The OE starter quit on me.  and in the worst part of town possible...  I didnt like my boss standing over me while i fixed it with a claw hammer and a 45.  but it was reassuring...     im glad somebody besides me had a gun...  cuz all i coulda done at that point with mine was shoot out the fender and floorboard if something hadda gone wrong...lol

[78 Chevyrado]

I know MPG will suck...  which setup will get me the best?   I drive 60-65MPH usually but sometimes I wanna get home quick, so I go with the flow and go 80MPH.  What will get me there the best?   I basically like to go with the flow weather its flow at 55mph, or flow at 80mph.   The cops around here run 80-85 and dont stop you unless you do something stupid like pass them, or such...

[Stewart G Griffin]

Is there any reason why you can't look for another truck with a 6.2?

[78 Chevyrado]

My being sentimental makes me wanna drive it.  It was the last truck grandad used when he quit building,  and id love it to keep on doing what it used to do.  I just think its cool is all.

[KWKENUF]

One thing that really stands out to me that has not been mentioned is your tires.  You have wide,  aggressively treaded BFG's,  and decently wide wheels.  Seriously think about going to a skinnier tire with highway treads.  If you could reduce the overall weight at the same time that will help even more.

I am thinking something along the lines of 235/85-16 with factory aluminum wheels,  PYO's I believe most people refer to them as,  would look good on your truck.  They will be easier for your truck to turn,  have less rolling resistance,  and probably be lighter.  It could also facilitate a small drop in height that could have a possible effect,  albeit not much.

When I had my 2005 Sierra,  I went from factory 265/70-17 Bridgstones to 285/70-17 BFG A/T's.  Bigger,  wider,  heavier,  and I lost 1-2 MPG's.

4x4 Garage did a test between the Michelin LTX M/S2 and the Dick Cepek FC-II's.  Same size tires,  285/70/17,  on a F-150HD.  On the 182 mile loop they drove,  the Michelin's delivered 17.16 mpg,  and the Cepeks delivered 14.93 mpg's.  That's a 2.23 difference!  This was in a controlled test,  and the article did state that they kept records for everyday mileage also,  and the difference was more like 1.75 mpg.

One other thing to keep in mind,  at 15,000 miles a year,  the difference between the 15 and 17 mpg is only $353 a year at $3 a gallon.  (the mags math,  not mine.)  If you are doing anything purely for mileage,  make sure you calculate the rate of return on your investment.  If your engine goes south,  then it really doesn't matter.

[Stewart G Griffin]

What type of fan you got?

[KWKENUF]

To get back to your original question about the engine itself,  have you checked out the 383HT?  I believe you said you are running the original 350 for your truck,  so I am going to guess it has a bad compression ratio (as in lower than advertised,  possibly sub 8:1),  not the most efficient heads available,  and old cam timing tech.   I can't remember specs off the top of my head,  but I believe it was 9:1 compression (will be more efficient than what you are running now),  L98 style heads (good for slow speed power and mpg),  and a cam that makes good low end power so you can run it at lower rpm's without lugging it.  It would be a straight forward weekend swap.  Pair that with an OD transmission,  electric fans,  different wheels/tires,  and every other mpg trick and over time I bet you could pull down some decent numbers.