Your MPG may never make the average (37MPG)

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Apr 9, 2007 | 10:57 AM

#11

SPL

Ridiculously Active Enthusiast

Joined: Aug 2006

Posts: 859

From: Waterloo, ON

Re: Your MPG may never make the average (37MPG)

If you doubt that temperature indeed has a major effect on fuel economy (mpg), have a look at the posts:
https://www.greenhybrid.com/discuss/...3&postcount=12
and
https://www.greenhybrid.com/discuss/...2&postcount=14
from another forum on this Newsgroup!

Also please note that any battery energy used by the air conditioning system has to be replaced, and so ultimately comes from the gasoline via the ICE (considering round-trip driving). Electric air conditioning isn't free!

Stan

Last edited by SPL; Apr 10, 2007 at 09:44 AM.

Apr 9, 2007 | 11:40 AM

#12

kdhspyder

Active Enthusiast

Joined: Jan 2006

Posts: 205

From: Two miles N of the technology 'center-of-the-world' in 1903, on the Outer Banks of NC

Re: Your MPG may never make the average (37MPG)

Quote:

Originally Posted by H2O Doctor

As an engineer and dedicated researcher on the TCH, I'm interested in the relationship between temperature and FE. I live in sunny Southern California so I have limited first-hand information. I do track the mileage on every tank and also note the % of time I travel on the highway as well as an approximate temperature for the tanks. I've developed a spreadsheet where I track this information.

However, the lowest temperature I have experienced was only 40 F and that for a short period of time.

A while back I tried to develop some approximations to define what temperature would do based on what others were reporting. I recognize that the length of the drive is a major determinant along with the amount of highway driving.

What I calculated was this:

80 F appears to be the ideal temperature for the TCH. Any higher and A/C begins to reduce mileage.

50 F seems to reduce mileage by ~5%
30 F seems to reduce mileage by ~10%
100 F seems to reduce mileage by ~8%

I only used data from those with at least a 30 minute average travel, and gave more weight to the information with those with a 60 minute commute.

I would be interested if anyone has any information which either confirms my calculations or shows that they are in error.

Posted previously here on another thread...

Factors affecting your FE ( and everyone else's also, btw ) in decending order of importance...
1) Towing anything is a huge penalty possibly as much as a 50% reduction in FE
2) Lots of weight in the vehicle, passengers cargo etc. ( EPA tests are done empty )
3) Short trips under 10 min - deduct 20% from your 'Norm'
4) Snow, Rain, sleet - deduct 15%
5) Strong head wind - deduct 10%
6) Cold weather - deduct 5 - 10%
7) High speed driving 0ver 70 mph - deduct 5 - 10%
8) Many starts from a dead stop ( going from stop sign to stop sign to stop sign ) - deduct 5 - 10%
9) Terrain - fortunately 'what goes up..' usually this balances out on a RT
10) Winter fuel - deduct 2 - 5%

Now these are cumulative, so short trips with a lot of stops ( -20% )( -5% ) in winter ( -7% ) on slick pavement ( -15% ) can result in as much as a 40 - 50% loss from your personal 'Norm'.

Apr 10, 2007 | 08:37 AM

#13

obrienklm

Enthusiast

Joined: Mar 2007

Posts: 31

Re: Your MPG may never make the average (37MPG)

The cold weather is a huge factor especialy during the first 10 minutes while the car warms up. In Minnesota, the 10% ethanol mandate is also a minor factor in the mileage one can achieve. Ethanol only contains about 85% of the BTUs of gasoline, so mileage with 10% ethanol would be reduced by a bit less than 2%.