Average Rotations per mile

[Drew Dowdell]

I think we need a different measure of how much a vehicle has been used rather than just mileage.   I'm sure we've all seen those ads for used cars saying "All highway miles!", but I think in addition to that, we have to start to take powertrain setup into consideration.

When I bought my Avalanche, it only had 12,800 miles on it which is insanely low for a 7 year old truck. But for all I knew, those could have been all city miles where the truck was idling and going through short bursts of acceleration. But I actually know it was mostly highway miles because these trucks also have an engine hour monitor on them.  I don't remember what it was when I bought it, but I think somewhere just over 400 hours.  It has 534 hours on it today.  That means for its entire life it has averaged 34 miles per hour. 

This is part of the reason I think we need a better measurement of vehicle use.

The other part is that on my suburban commute to work, I rarely break 2,000 rpm, but in the Encore, I was regularly going well over that because the little 1.4T had to work so hard compared to the 5.3 in the truck.  A hybrid or Voltec powertrain also changes the calculus.   I am helping my part-time employee pick out a new to him car and I've semi-sold him on a used Volt.  I had to explain to him that the Volt motor only runs 50% of the time, so a higher mileage example is still okay.

I think some sort of calculation for this should become standard.  Probably a function of (Average RPM per mile * miles)/engine hours.  This would give you a better idea of how hard the engine worked and for how long rather than the somewhat meaningless miles.

[balthazar]

'All highway miles' is actually worse; higher RPM = more wear.
Start/stop sequences are also high-wear scenarios.
Lots of 'heat up / cool down's also not ideal.

Not sure if there's an answer here.

[Robert Hall]

Hour meters are a neat feature.  I’ve seen them on heavy trucks and tractors.  The WK2 Grand Cherokee had one in ‘11-13, was dropped for ‘14. 

[Drew Dowdell]

2 hours ago, balthazar said:

'All highway miles' is actually worse; higher RPM = more wear.
Start/stop sequences are also high-wear scenarios.
Lots of 'heat up / cool down's also not ideal.

Not sure if there's an answer here.

The point about the highway miles is more about the difference between a 5.3 V8 at a 70 mph cruise turning 1700 RPM and a 1.3T I3 at 70 mph cruise turning 3,000 rpm.

Driven the same way over the same distance, the I3 will have made ~double the number of revolutions.

It’s that discrepancy I’m trying to capture.

[balthazar]

^ Gotcha.
Kinda doubt with today's mega-gear trans that anything would actually turn in the neighborhood; my B-59 with a 3-spd auto and 3.73 gears will be doing about 2520 RPM @ 60 (and I was contemplating an OD unit because of that).

[USA-1]

Same reason Corvettes get such great mileage on the hwy. power/weight ratio. I've gotten 30-32 mpg cruising at 75-80 mph Phx to Vegas and there's some elevation change as well. At 80 mph I'm at 1,800-2,000 rpm. Now my old square body 3/4 ton I had with 350cid 4bbl, TH400 3 spd. with 4:10's I was at 3,000-3,200 rpm at 65 mph and regularly got 9 mpg whether towing or not.

Another reason Ford EcoBoost in the F150 doesn't get any better mpg's sometimes even worse than a GM Silverado/Sierra competitive V8 does. That small V6 is working a lot harder, the turbos are stuffing the air and fuel in.  

[Drew Dowdell]

9 minutes ago, USA-1 said:

Same reason Corvettes get such great mileage on the hwy. power/weight ratio. I've gotten 30-32 mpg cruising at 75-80 mph Phx to Vegas and there's some elevation change as well. At 80 mph I'm at 1,800-2,000 rpm. Now my old square body 3/4 ton I had with 350cid 4bbl, TH400 3 spd. with 4:10's I was at 3,000-3,200 rpm at 65 mph and regularly got 9 mpg whether towing or not.

Another reason Ford EcoBoost in the F150 doesn't get any better mpg's sometimes even worse than a GM Silverado/Sierra competitive V8 does. That small V6 is working a lot harder, the turbos are stuffing the air and fuel in.  

Exactly! Those small turbos work a lot harder and turn higher rpm to keep up. 
that’s why I think comparing mileage doesn’t tell the whole story.

Bring in something like Voltec or any other plug in hybrid and the matters are even more complicated