Increased Fuel Economy, Am I Crazy?

[oosik]

I have a 2018 Ram 2500 HD Power Wagon. 35K miles. I normally average - 16.5 mpg. If I watch my speed OR drive with the wind - I can get 20 mpg. Drive against the wind or over 70 mph - I'll be lucky to get 13 mpg.

Drive against the wind AND over 70 mph - better know where I am and where the gas stations are.

 

[mjonesnh]

Not as drastic as your experience. Ran Motorcraft 5w20 Synthethic blend from new till this spring in my 17 Ford Escape. Switched to Mobil 1 Extended Performance Full Synthetic 5w20 and my mileage went from 27.7 to 29.9, a gain of 2.2 mpg more per gallon mostly local driving. On a trip of 300 miles the difference goes to 3.0 more per gallon. Almost 10% difference just by changing oil brand in same weights.

 

[DarkBlack]

and for some reason when it is raining seems to drop mileage even if there is no extra wind.

It takes energy..power, to move water. Every raindrop is smacking your vehicle and being instantly accelerated to your vehicle speed. This takes energy.
Your tires are plowing through water on the road. Ever check the mileage of boats?. It takes energy to throw that rooster tail of water spray off each tire. Try physically throwing water up with your cupped hands, like your tires do during rain, for a few second and see if You don’t get tired

 

[ArlyA]

Not sure air temps were mentioned by the OP.
-----------------------------------------------------
Air temperature has a significant impact on a vehicle's fuel economy:

• Cold weather
  Fuel economy can drop by 15% in the city and up to 24% for short trips when the temperature is 20°F compared to 77°F. This is because:
  The engine needs more time to warm up
  
  • 
    
  • Engine oil and drive-line fluids are colder, increasing friction
    
    
  • Tire pressure is lower, increasing rolling resistance
    
    
  • 
    Aerodynamic drag increases due to denser air
    
    
    

 

[LittleBittyBigJohn]

Not sure air temps were mentioned by the OP.
-----------------------------------------------------
Air temperature has a significant impact on a vehicle's fuel economy:

• Cold weather
  Fuel economy can drop by 15% in the city and up to 24% for short trips when the temperature is 20°F compared to 77°F. This is because:
  The engine needs more time to warm up
  • 
    
  • Engine oil and drive-line fluids are colder, increasing friction
    
    
  • Tire pressure is lower, increasing rolling resistance
    
    
  • 
    Aerodynamic drag increases due to denser air
    
    

This is for sure a possibility. We are entering fall now.

Otherwise my driving habits have remained the same.

 

[nyone]

I’m not a gas mileage freak but out of something to do I track it on longer trip. I hated the 55 mph speed limit when it was a thing but it does make a big difference on fuel mileage. It’s also something you can control. Driving 65 mph vs 75 mph makes a difference. I drive a little over the speed limit but driving on a 2 lane road you are usually driving slower.

Tailwind will really boost your mileage. If you have a 15 mph tailwind and are driving 75 mph your vehicle thinks it going 60 mph as far a wind resistance and fuel mileage.

I find this to be quite opposite with My 2012 suburban. The 6.0l and 6speed seam to like 75-80mph quite a bit more than 55-65mph. I got 3mpg better between 75-80mph, calculated not via the dash.

 

[dodge man]

I find this to be quite opposite with My 2012 suburban. The 6.0l and 6speed seam to like 75-80mph quite a bit more than 55-65mph. I got 3mpg better between 75-80mph, calculated not via the dash.

I’d say that’s an unusual case. Wind resistance is exponential based on your speed.

 

[jonsstihl]

yes, force required goes up with the square of the velocity.

My coworker has a 2023 sierra with the 5.3L and he said the same thing. we think it has something to do with the transmission not making it into 10th gear at slow speeds but once you get above 75mph it gets there.

 

[Jstpssng]

I found that my old '98 Sierra with 4.3 V6 got it's best mileage at around 65. As already mentioned, it stayed in high gear at that speed.
Conversely, as it got older cold weather really affected it. One cold snap we had it kept tripping codes, just because of the weather.

 

[Renze]

I guess if they put some heavier 15W40 oil in, it might be a mpg gained switching to 5W40, especially if you have lots of shorter trips where the oil spends most of the time warming up.

On my 2007 V70 diesel, switching from 0w/30 fuel saving lightweight formula according to manufacturers recommendation, to 10w/40 Castrol wear diminishing formula, my oil consumption went from 1 liter per 3000km, to 1 liter per 30.000km

Fuel consumption i never compared, giving the cost of 0w/30 the savings on oil are greater than the savings on fuel. I do 50mpg anyways.

Also, after an oil change on saturday and a short trip to my parents on sunday, say 20 minutes of running to distribute the anti wear film on all the rotating components, on monday morning cold starting after a mild frost, i could hear the difference, it didnt take 20 seconds of clattering before sounding right.

In fact the 2006 model year had problems with cam and follower wear, it was the first year they started prescribing 0w/30. My 2007 already has a cam with better hardening.

Fuel saving long life oils are invented for the bean counter selecting a company car based on average fuel consumption and average maintenance cost up to 200.000km when lease cars get dumped into the used car trade.

But if you want to drive beyond 600.000km you better get rid of that fuel saving junk because it is not saving engines...

A contractor here, his Fendt 818 had 500hr oil change intervals. He changed every 250hrs because the oil smelled and looked not OK at 500hrs.