what caused my 3 mpg increase?

[Errtt]

A previous vehicle - I got new tires that were LRR and expected maybe a little better MPGs.
I actually lost a little MPGs and at the time the fuel blend (winter<>summer) didn't change or anything else noticeable like driving conditions or weather. Turns the LRR wasn't giving me an increase for the couple years use.

 

[Alex_V]

My vote is tires and valves, in that order.

 

[KneeGrinder]

Tires, valves, and also the pacific north west has been fairly warm this past month, warmer than usual. Also, dryer roads in my area, which means less rolling resistance. Just be happy and "roll" with it!

 

[JLTD]

Definitely the valves. I once owned an old Plymouth with solid lifters, and tracked mpg religiously. With every valve adjustment (about every 20k miles) I noticed a similar uptick in mpg. Also got real good at valve cover gaskets on that 225 Slant Six.

 

[bbhero]

Yeah that would make more sense to me as well CharlieBauer. I would think brand new tires would drop gas mileage to having to travel greater distance per rotation of the tire. That distance per rotation would or could be quite a bit depending upon how old and little tread life was left on the old ones versus brand new tires and how thick they would be. I had a set of Goodyear Assurance tires that were at 77k miles... Trust me the difference in tread depth between them and the new Cooper Ultra grand touring ones was quite a lot.

 

[Rolla07]

Originally Posted By: barryh
Leaving differences of rolling resistance between two different makes of tire aside, rolling resistance increases with tread depth so new tires seem unlikely to have contributed to the improvement in MPG, quite the opposite.

Not sure what you mean by valve adjustment but on old engines without hydraulic lifters changing the valve clearances makes small but real changes to valve timing, lift and most important for low rev efficiency - overlap.


+1

New tires should reduce mpg not improve it, if the previous tires were worn out.

Id vote the valve adjustment. Just cuz oil is unlikely to have changed it.

 

[demarpaint]

I'd say a combo of the three, the tires probably being the #1 contributor, unless the valves were way out of adjustment. The oil contributing the least.

 

[Vikas]

Hold on a second

Quote:
am at 22.7 over 20 miles 50/50


Are you telling us that this is all based upon your 20 miles of data?

 

[gathermewool]

Originally Posted By: Vikas
Hold on a second

Quote:
am at 22.7 over 20 miles 50/50


Are you telling us that this is all based upon your 20 miles of data?


Good catch! However, we all know that 20 miles is a 100% sufficient amount of data....

....

 

[WhyMe]

Originally Posted By: Vikas
Hold on a second

Quote:
am at 22.7 over 20 miles 50/50


Are you telling us that this is all based upon your 20 miles of data?


No this just happened to be what was showing at the time that i put the gas in on that day . i have 3 full tankfuls of data .

 

[mcrn]

Lighter tires...the rt 43's are pretty light tires.

 

[Vikas]

The thing is with that kind of improvement, it should be apparent just by throttle response and general driving. If so, I would attribute it more to valve adjustment than tire or oil change. Also is it possible that your are changes gas formulation around this time? At least for me, the difference between summer/winter gas is excess of 10% on all of my cars with similar driving patterns.