2006 CC Lariat 4X4 6.5' bed 5.4L

I decided to run my truck on Shell 93 octane and I gained 1.6 mpg. I used to get 13.7 on discount gasoline, but now I'm up to 15.3 on the same drive and the same conditions. I have a lead foot and usually travel around 75-80 on the interstate.

I drive 1000 miles a week so I'll continue to do this for a month or so and see how things go. This is the 3rd week of me doing this with the same results.

I made a program in excel that would calculate how many mpg I would have to gain in order to break even. Well, the more expensive regular gas is the cheaper it becomes to run on premium. Let me explain. Keeping a .30 cent difference between regular and premium.

All calculations based on 1000 miles of driving.

$1.50 reg 13.7mpg 72.99 gals used
Total=$109.49

$1.80 prem 15.3mpg 65.36 gals used
Total=$117.65

More realistic gasoline prices.

$2.80 reg 13.7mpg 72.99 gals used
Total=$204.38

$3.10 prem 15.3 mpg 65.36 gals used
Total=202.61

This was very interesting to me. You only realize the the benefits of switching to premium when regular gas is around $2.60. Any lower and it really won't make much difference. When regular gas gets higher thats when premium makes sense. I was surprised by this result.

 

Very interesting. I wonder if anyone else has noticed an appreciable difference in fuel ecconomy between regular unleaded and premium with the detergent load.

Simply put, Shell, Chevron, Texaco, etc... premium 93 octane fuels are the ones that load up on additives and detergents to keep your top end clean.

I almost wonder if running the high detergent gas would be a benefit to 5.4L 3V owners like myself in regards to the spark plug issue...

BTW, I would pick Chevron or Texaco over Shell anyday... But that is more due to offshoring of labor issues than any thing else...

 

i actually noticed an increase from going from Shell's 89 octane to their 87 octane. I use to get around 12 but now i get about 13...and even got 14 on the last tank.

i might have to try the premium gas now.

 

I've never used premium fuels till now. I saw no reason to try them, because the manual said that 87 octane was just fine. I guess these newer trucks really can benefit from premium fuels.

I'll try out different brands and see how they do over the next month.

 

I also tried Shell 93 octane in my 2004, 5.4. Got a gift card for fathers day and decided to throw the 93 into my truck as it supposed to clean the engine and run better. I noticed that my gas gauge was not moving after using the 93 compared to the 87 octane which really seemed to go right through the truck, if it's true about being cheaper to use the 93 octane this would be a no brainer........

 

higher octanes burn slower than lower octanes. the piston is only at TDC for a certain amount of time. you'll have an incomplete burn with higher octanes, so i don't see exactly how your mileage went up. did you do your comparison with Shell 87 vs Shell 93, or Mom and Pop station 87 vs Shell 93. the difference could be in the quality.

 

Your analysis is very informative, and because you covered 1000 miles, very believable. I am going to experiment with it.

I know that in my boat, which has a 5.0L V8 with two-barrel carburetor, if I decide to use 93 octane, I have to set the timing (by hand) to 10 degrees. If I decide to use 87 octane, the timing has to be a few degrees more. This is old technology. The new technology has knock sensors that can auto adjust the timing.

The higher the octane, the more precise the timing of the detonation, so the tighter timing can be set. The tighter the timing -- the more horsepower and fuel economy. I always though that in miles per dollar, 87 octane will always win -- but now am having to rethink the issue. I prefer 93 octane because it is cleaner burning.

 

You won't see incomplete burning because of higher octane. Does not work that way. The burn times are very fast, even when the higher octanes are considered slow. What you will reduce or eliminate is preignition and knock. Here's a primer:

http://auto.howstuffworks.com/question90.htm

 

I gained 2 MPG by taking the lead out of my shoe.

 

I'll have to try this too.
I remember years ago when I had a 91 Explorer and gas was cheap. I switched to premium because of a rotten egg smell it had in the winter.
The smell went away and the mileage went up, but doing the math it was the same price for miles driven.

I thought your .30 cent price difference didn't make sense so I check on "gasbuddy.com" and the price for premium around here is only .20 cents higher then regular. So the savings will be even higher.

 

Everything about your calculations makes no sense, your comparing the mileage you got with discount fuel to the mileage your getting with quality fuel. You would have seen the same increase by switching from discount to Shell 87. The 3v 5.4 runs a compression ratio that allows for use of everything from 87-93 octane. It really doesn't matter which grade you use, it's the quality/purity of the fuel that makes the difference.

 

in my 2005 XLT Scab 4x4 with the 4.6. This is on 87 octane Shell. The reading before that was right on 19.

 

I get about the same mileage on what ever brand I put in my truck it is only the rare times I'm easy with my right foot that mileage increases in my truck.

 

How you drive will always have the biggest impact on MPG. I used to make sure to keep it around 2000 RPM and thought that was the best way to get the most out of my fuel. Recently I've noticed that if I get up to speed quickly then get the RPM down to cruising range, I'm seeing an increase in mileage. It's not a big increase, 1-2 MPG, but still an increase. I use Shell 87 BTW.

 

Since an engine is always most efficient at WOT, it does make some sense to quickly accelerate and then let up, at that point making sure you are keeping under 2000 rpms.

Another thing I've noticed is that these trucks coast really well. For instance, I can coast halfway thru town on my way to work in the morning, after I climb a slight hill. So if you get your foot off the gas as soon as you crest a rise, you can often go a long way while your engine is idling.