Gas Mileage

[Quattro Pete]

Originally Posted by fdcg27
I think that most people who actually care are already aware of this, but the point is that the more efficient vehicle always saves its driver fuel and money.

For sure, but it would be helpful to understand just how much the true savings are, if that is what is being used to justify the purchase of a new vehicle.

 

[Al]

Quattro. Lol your 25% is based in comparing th difference to the gas hog. But if I drive the XV I go 33 % further than the gas hog. Where as if I drive the hog I would be saving 25% (of my cost) by driving the XV. Don't feel bad you are in a lot of company

 

[Quattro Pete]

Originally Posted by Al
Quattro. Lol your 25% is based in comparing th difference to the gas hog.

The 25% is based on the MPG figures you initially provided: 21 vs 28.

Later you came back and wrote that it was actually 24 vs 31, which would be a 23% difference in fuel consumption.

Quote
But if I drive the XV I go 33 % further than the gas hog. Where as if I drive the hog I would be saving 25% (of my cost) by driving the XV.

I'm not quite following you there.

Anyway, I'm not questioning that the XV is more economical. I was just trying to make sure we calculate those differences correctly.

Enjoy your new ride. Happy Memorial Day!

 

[Al]

Depends which vehicle you use in the denominator.

Happy Memorial Day to you also..

 

[Quattro Pete]

Originally Posted by Al
Depends which vehicle you use in the denominator.
Your old (original) vehicle goes in the denominator because that is your reference point, so in this case it would be your Forester.

But it's what you put in the denominator that matters, as I explained earlier.

Going from 24 MPG to 31 MPG is a 29% improvement in MPG, but only a 23% improvement in actual fuel consumption (fuel savings).

 

[fdcg27]

Originally Posted by Quattro Pete
Originally Posted by fdcg27
I think that most people who actually care are already aware of this, but the point is that the more efficient vehicle always saves its driver fuel and money.

For sure, but it would be helpful to understand just how much the true savings are, if that is what is being used to justify the purchase of a new vehicle.


You're right and the answer does lie in simple math which many probably overlook.
This is something people need to consider when paying more for a vehicle simply for the savings in fuel.
Fuel used over distance traveled is what actually matters and that has to be calculated based upon expected fuel economy.

 

[Ws6]

I think this is an incidental finding. A Forester 2.0XT customer is not also a XV customer, unless it is for a second vehicle, as a XV will not do what the 2.0XT will in any shape, form, or fashion. If one buys an XV or XV instead, the mpg will be incidental.

 

[Al]

Originally Posted by Ws6
I think this is an incidental finding. A Forester 2.0XT customer is not also a XV customer, unless it is for a second vehicle, as a XV will not do what the 2.0XT will in any shape, form, or fashion. If one buys an XV or XV instead, the mpg will be incidental.


You are changing numbers on me:

This is what you said:
"In reality, a jump from 21 MPG to 28 MPG is only about 25% savings, not 33% that the MPG math would have you believe."
I can't figure for the life of how you can say when I drive only 21 miles in my XT and then jump in my XV and go 28 miles that I am not geting 33.3% better economy

..Perhaps someone else can explain it to you..Have a holiday beer my friend..that what I doing.

 

[Smokescreen]

https://ecomodder.com/forum/EM-hypermiling-driving-tips-ecodriving.php

Any vehicle I own gets better than EPA ratings....90% is in technique.

 

[Quattro Pete]

Originally Posted by Al

You are changing numbers on me:

This is what you said:
"In reality, a jump from 21 MPG to 28 MPG is only about 25% savings, not 33% that the MPG math would have you believe."
I can't figure for the life of how you can say when I drive only 21 miles in my XT and then jump in my XV and go 28 miles that I am not geting 33.3% better economy

..Perhaps someone else can explain it to you..Have a holiday beer my friend..that what I doing.

I already explained it here: https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/5116318/re-gas-mileage#Post5116318

You need to convert MPG to gallons per 100 miles if you want to talk about actual fuel economy improvements and savings, and not just MPG improvements.

 

[supton]

Originally Posted by eljefino
My prius is set up for slower= better. I've pulled some amazing MPG stuck behind a school bus.

We went on a family trip to DC several years, my Tundra pulling a small popup camper. I got great results drafting semis. I tried drafting a Prius and it didn't seem to do much...

 

[Benzadmiral]

As for me, I'm astonished at what the turbo 4-cylinder in the BMW can do. Not only does it have speed aplenty on tap, but tremendous efficiency for a fairly heavy car. I've been seeing anywhere from 25 to 28 mpg depending how much highway I get in during the ~12 days between fillups. Yesterday's 80-mile highway trip (with A/C on, one passenger, speeds from 60-70 to the occasional 80 for passing) brought the average for this period up to 32.5.

None of my previous cars, including the 4-cylinder Benz and the 4-cylinder Buick, could match this. I have to run premium, yes, but the BMW's mileage increase over the Buick's mpg almost washes out the price increase of 93 over 87 if I purchase carefully.

 

[RDY4WAR]

I've been calculating it lately as gallons consumed per hour of driving.

I drove a 400+ mile stretch with the cruise control set at 60 mph and again at 75 mph, dividing the mileage by how many gallons it took to top off at the other end.

At 60 mph, it showed 21.87 mpg.
At 75 mph, it showed 18.33 mpg.

60 / 21.87 = 2.74 gallons per hour.
75 / 18.33 = 4.09 gallons per hour.

A 49.3% increase in fuel consumed per hour.

At 60 mph, it took 6 hours and 45 minutes.
At 75 mph, it took 5 hours and 24 minutes.

6.75 x 2.74 = 18.49 gallons
5.40 x 4.09 = 22.08 gallons

22.08 - 18.49 = 3.59 gallons

3.59 × $2.50/gal = $8.98

It cost me $8.98 to save 1 hour and 21 minutes on that trip.

60 mph = 1577 rpm
75 mph = 1971 rpm (+25%)

A 25% increase in rpm with a 49.3% increase in fuel consumed per hour. That's a pretty clear indication that the engine is under a lot more load at 75 mph than 60 mph.

Moral of the story. Wind drag sucks.

 

[supton]

Originally Posted by RDY4WAR
It cost me $8.98 to save 1 hour and 21 minutes on that trip.

2.74 GPH is $9.84 per hour cost, while 4.09gph is $14.68 per hour. Or an extra cost of $4.84/hour to save 25% of your time spent. [Technically tires should wear faster, as should the oil and bearings and whatnot--but I suspect their cost pales in comparison to the fuel burn.]

I guess it comes down, what's the value of your time. A few bucks here, a few bucks there could add up to serious money over a year. OTOH on a once in a great while trip it sounds like it cost you $9 give you an extra hour 21 not sitting in a car.

 

[Quattro Pete]

Originally Posted by RDY4WAR
I've been calculating it lately as gallons consumed per hour of driving.

I drove a 400+ mile stretch with the cruise control set at 60 mph and again at 75 mph, dividing the mileage by how many gallons it took to top off at the other end.

At 60 mph, it showed 21.87 mpg.
At 75 mph, it showed 18.33 mpg.

60 / 21.87 = 2.74 gallons per hour.
75 / 18.33 = 4.09 gallons per hour.

A 49.3% increase in fuel consumed per hour.

At 60 mph, it took 6 hours and 45 minutes.
At 75 mph, it took 5 hours and 24 minutes.

6.75 x 2.74 = 18.49 gallons
5.40 x 4.09 = 22.08 gallons

22.08 - 18.49 = 3.59 gallons

3.59 × $2.50/gal = $8.98

It cost me $8.98 to save 1 hour and 21 minutes on that trip.
The above example works nicely with gallons/100 miles as well.

21.87 mpg = 4.57 gal/100 miles
18.33 mpg = 5.46 gal/100 miles

This means your fuel economy at 75 mph is 19.31% worse than at 60 mph ((5.46-4.57)/4.57), which means that driving that same route at 75 mph will cost you 19.31% more (in terms of total gallons consumed and therefore in dollars as well).

4.57 gal/100 miles over a distance of 405 miles = 18.52 gal; $46.30 total cost
5.46 gal/100 miles over a distance of 405 miles = 22.09 gal; $55.24 total cost

 

[gofast182]

One of the best fuel efficiency stories is our new 2019 BMW X5 40i. This thing weighs 5,000lbs (wow) and is powered by the B58 I6 turbo and driven by the ZF 8AT. We get 24mpg around town, 29mpg on the highway, and I got 14mpg towing a 4,000lb trailer & car. To me it is astonishing that a big heavy SUV like this can return those numbers, plus it's fast when you want it to be!

 

[Quattro Pete]

Originally Posted by gofast182
One of the best fuel efficiency stories is our new 2019 BMW X5 40i. This thing weighs 5,000lbs (wow) and is powered by the B58 I6 turbo and driven by the ZF 8AT. We get 24mpg around town, 29mpg on the highway,

That is very impressive. Wife's Q5 weighs less, yet you'll only get about 18 mpg around town.

 

[SubieRubyRoo]

Al, I just tagged another 380 miles of mixed (probably 60% highway) on 12.223 gallons in the Impreza, for a Fuelly-calculated average of 31.1mpg. Amsoil ATM just crossed 2k and no change in level either, so it looks like I'm on for the 10k sample with no drain, and swap to the Microgreen to pit the XG vs MG on PC. Enough acronyms for you? LOL

 

[Skippy722]

Before we moved, I had a 10 mile commute... babying the car as much as I could I was just hitting 23mpg. I now drive 20 miles mostly highway, and driving a little more normally (okay, spirited at times), and I'm getting 27. Bet I could hit or break 30 if I baby it again

 

[MCompact]

Today there was little traffic on my 12 mile commute, and almost every traffic light was green. The result was that the Clubman returned 49.7 mpg(adjusted- as the OBC is 5% optimistic). The drive home was a bit more congested so adjusted mileage for the round trip was 42.0 mpg.
I'll take it.