Are MPG ratings much less accurate then they used to be?

I thought the ratings were done on a flat road on the moon where there is
1/7th the gravity in order to get those MPG results.

I never thought they were very accurate, I only use them to compare one
vehicle with another to get a relative ranking when I do a vehicle purchase.

 

I remember way back when I used to do my own tune up, timing and all. Now I
don't even recognize what is under the hood.

 

It depends on your driving conditions. Every vehicle I've owned in the
last 20 years has obtained within 10% of the EPA ratings. I drive a mix
of highway and city, but mostly highway (80%). I tend to get very close
to the EPA highway ratings and almost never get anywhere near the lower
city ratings.


Matt

 

The difficulty is in the stackup of assumptions and calculation margins.
The MPG protocol, believe it or don't, amounts more or less to "Let's see,
we measured *about* such-and-such percent HC and CO in the exhaust, and
the catalytic converter efficiency is *about* such-and-such percent, so we
can assume that *about* such-and-such amount of CO and HC is coming off
the manifold, which would mean that *about* such-and-such an amount of
fuel was burned".

Never mind that simply measuring the liquid volume of fuel before and
after the vehicle is run is considerably easier, more direct, more precise
and more accurate, that's not how it's done.

 

they are not far off problem is people do not go the 55 mph the calulations
were done at
they still use the old standard of 55mph being the national speed limit and one
i feel we need to go bac to so gas starts to stack up at the refineries and
watch how fast the price comes down

 

"I can't drive ... 55"



Gary