Not only was the mileage better, but the 81 felt doggy compared to the 82, the 300 liked the 2.75's better if that makes any sense.

 

This ratio most likely had the engine RPMs in the "sweet spot" [maximum torque] at your desired cruising speed.

 

It wasn't just at crusing speed, it was in general, something in my setup made it behave better when it was loaded down, almost like a turbocharged setup.
I'll have to find my cam card if I still have it and run it in engine analyzer but I seem to recall it having a plateau from 2000-2500, so with 3.50's it still should have been in the sweet spot.

 

Okay, a gas mileage update and comparison to previous years...

3/12/08 - 3/9/09; 7774 miles; $2.899/gal. avg.; 15.88 mpg
3/17/09 - 3/16/10; 9094 miles; $2.329/gal. avg.; 16.21 mpg
3/18/10 - 3/12/11; 8410 miles; $2.639/gal. avg.; 15.91 mpg
3/22/11 - 3/10/12; 8043 miles; $3.409/gal. avg.; 15.74 mpg
3/18/12 - 3/6/13; 9981 miles; $3.329/gal. avg.; 16.50 mpg
3/14/13 - 3/11/14; 8161 miles; $3.169/gal. avg.; 15.16 mpg
3/18/14 - 3/7/15; 9710.9 miles; $2.929/gal. avg.; 18.87 mpg
3/17/15 - 2/4/16[current]; 8940.7 miles; $2.039/gal. avg.; 19.99 mpg

The records started when I purchased the truck from the original owner [March, 2008].

When thinking about the last two entries, bear in mind that MPG goal oriented work was done as a collective effort while attending the OK GTG [9/13/14 & 10/3/15].

 

I saw your PM. Thanks for the heads-up.

Well, if the change to synthetic lube did any good then you don't have the full effect yet in the annual average since it has only been 4 months. So, your average should top 20.00 pretty easily this time next year.

 

Odd that your worst mpg average (15.16 mpg) was observed relatively late in the record (3/13-3/14). I wonder why.

 

I do not have my records with me, but think I have most of the details in memory.

Prior to that time, I used a carburetor from a 1982 4.9L engine. I could not use the vacuum advance because it caused the timing advance to be too great and the engine bucked like crazy under light load @ ~1600-1800 RPMs. This was due to the fact that I crossed the leads, from the distributor, to the MSD box. This was done back in 2008 and in an attempt to compensate, I adjusted the initial timing very high [occasional dragging when starting] and did other things to increase mileage. Then, in late 2012 or early 2013, I replaced the carburetor with one from a 1970 F350. This carburetor has one vacuum port and when connected, the bucking had stopped and the base timing was backed off. So, I drove it like that until one day while checking timing via the vacuum gauge technique, it was discovered that this vacuum port has ~5" vacuum @ idle and never goes higher than ~11". So, that is why the bucking had stopped, but the timing never advanced far enough at cruise conditions to give the best gas mileage.

By late 2013 or early 2014, I corrected the MSD wiring and plumbed the vacuum advance to the manifold. At that point, the OK GTG gurus literally placed their hands on the ignition and carburetion system and that is why the gas mileage increased significantly.

 

3/17/15 - 4/11/15; 10059.0 miles; $1.999/gal. avg.; 19.27 mpg

At the end of the previous post [2/4/16 & high lighted with red], I posted what was current at that time. The average gas mileage ended up being less [19.27 vs. 19.99] due to a couple of weeks of cold weather with the resulting drop in gas mileage. I am happy to report that the weather has moderated and gas mileage has now improved!

2/13/16; 17.30 mpg; town / 26-60F
3/03/16; 17.41 mpg; town / 34-72F
3/12/16; 19.43 mpg; town / 45-78F
3/22/16; 19.98 mpg; town / 33-86F
4/01/16; 19.87 mpg; town / 38-75F
4/11/16; 18.28 mpg; town / 38-75F

The next two data entries were not figured in the 3/7/15 - 4/11/16 yearly average since they are the first two tanks of the next yearly span, which is based on the purchase date of the truck.

4/21/16; 20.08 mpg; town / 45-80F
4/30/16; 20.34 mpg; town / 55-85F

 

 

I was getting ready to put away my records and a thought occurred to me. It is one thing to average the gas mileage during a set period of time, as I have done and will continue to do, but I reviewed the data for the same time periods [1 year] which Gary has for us to see in his graph [thanks, Gary] and am going to list the single lowest and highest gas mileage recorded during those periods. Perhaps this will tell us something?

March 2009; low = 9.40 mpg; high = 21.83 mpg
March 2010; low = 13.58 mpg; high = 20.04 mpg
March 2011; low = 13.40 mpg; high = 20.77 mpg
March 2012; low = 14.54 mpg; high = 20.54 mpg
March 2013; low = 14.56 mpg; high = 22.28 mpg
March 2014; low = 12.53 mpg; high = 19.53 mpg
March 2015; low = 16.80 mpg; high = 23.37 mpg
March 2016; low = 17.15 mpg; high = 25.72 mpg

 

So looking at the graph (thanks Gary) it shows a big jump in MPG from 3/14 to 3/15+
Looking at the numbers you (me) just don't see that.
What was done to get that big a change, way you drive, motor or drive train change?
Dave ----

 

FuzzFace2, a couple of things come to mind... go back to my answer to Galendor's question [2/15/16 post]. That will help to understand the initial upward shift. Then, at the 2014 OK GTG, work was done to optimize the ignition timing. This consisted of decreasing the static timing and adjusting the vacuum canister on the distributor so the vacuum assisted timing increase would initiate sooner. This was then adjusted more, in steps, by me after returning to my home base. Adjustments were made after each tank of fuel, making sure there was no pre-ignition detected.

For the 2015 OK GTG, aerodynamic modifications were made to my truck prior to the drive to OK [~625 miles].

The overall yearly gas mileage averages for 2014 and 2015 are skewed due to the extended highway driving conditions incurred with the drive to and from OK. The ~1300 miles of this type of driving [cruise] makes up approximately 10% of the total for those years. Prior to that [2009 - 2013], there was some highway driving for each year, but not this much.

That is why I felt the need to post what I did yesterday. If you ignore the highest gas mileage figures and just look at the lowest recorded figures, you will still note a marked increase for the years of 2015 and 2016. These "low" figures are based on a very repeatable driving routine and are not skewed by highway cruising.

The increase for the "low" mileage is based on the adjustments made in timing as well as part of the "aerodynamic" package still being utilized.

Thank you for your interest!

 

Thank you for the answer. Gives me something to look at when I get my truck on the road.
I did buy it for the 300 thinking it would be better on fuel than my 2002 DD 360 v8
Dave ----

 

Today will be a "mini update".

A couple of weeks ago, I had a flat tire. It could be repaired, but the treads were showing some wear [not yet to the wear bar indicators, but getting there]. I checked my records and the Michelin tires had delivered 60,000 miles and were 6 1/2 years old. I decided to give them to a friend who has a 1968 Ford Galaxie and just needs some good tires to use to roll the car around in the shop while he is working on it. They will do just fine and he was happy!

Unfortunately, Michelin has discontinued manufacturing a tire in this size, so I now am wearing a new set of Kumho Solus TA11. Only time will tell how they perform and wear. They do ride quite well.

While making this change, I decided to mount the tires on an old set of factory alloy rims which came off a 1995 F150. Boy, what a difference in weight. I did not actually weigh them on a scale, but the difference is quite apparent when lifting the tire/wheel combination.

In late September, I hope to attend the 2016 OK GTG in Skiatook, OK. The ~600 mile [one way] drive will give insight to how this combination does on the highway.

 

Plan on Sept 17th, although the last nail hasn't yet been driven all the way in. Someone "up north" complained about it getting cold the later we go, so the 17th is as early as I can make it.

Anyway, the weight difference with alloy wheels is quite noticeable. In larger sizes, like 35's, the guys say the weight/mass makes a big difference in power. So, you may see some in MPG, especially with your typical driving, although the shouldn't be much difference on the highway. At least, not from what I think the variables are.

And, glad you have good tires for the trip.