Last post on Feb 19, 2012 at 11:53 AM
You are in the Hyundai Elantra
What is this discussion about?
Hyundai Elantra, Hatchback, Sedan
#4911 of 4930 Re: MPG rating question [ [4ruth]
Sep 27, 2006 (11:40 am)
I am wondering whether the great mileage that we are supposed to be getting is based on actual calculations or on these meter readings.
I've done it both ways (and I owned a '01 Elantra for over 5 years that had no mpg meter), and I think it's very strange that you cannot average over 30 mpg under the conditions you described. The only thing I can think of is that you tend to drive with a "heavy foot." I've noticed huge differences in fuel economy with just slight differences in pedal pressure. Just today, I was driving a rental Impala on freeways. It has an instantaneous mpg meter (wish the Elantra had that). By just letting up on the gas pedal a very, very small amount I watched the instantaneous mpg jump from around 30-32 to upper 30s or low 40s (this was at 60-65 mph, level terrain). If I pressed just a little harded, the car didn't go any faster (maybe another 1 mph) but the mpg dropped. Try pretending that there is a raw egg between your foot and the gas pedal. Also keep your foot off the gas as much as possible--I think this is called "pulse and glide".
#4912 of 4930 Re: MPG rating question [ [4ruth]
Sep 27, 2006 (11:56 am)
I don't have the trip computer so all my calculations are the old-fashioned way.
I've gotten between 21 and 35 mpg since getting the car new, for an average of about 26 and a half. In mixed driving with AC on, I get about 25 or so; with AC off (even with windows down), I get 27-28.... provided I use the raw egg approach described above. If I lean into a little, that goes down, but still not too much.
My last car was a Ford Aspire, so I don't feel I need a lot of gas to get where I'm going; I glide around pretty good. My best trick for mileage is when I get on the freeway I try to use steady acceleration to get up to about 50-55 mph by the end of the ramp, then slowly blend into traffic at about 63 and set my cruise. I find that by not trying to be up to full cruising speed by the end of the ramp, I barely need to touch the accelerator.
#4913 of 4930 Re: MPG rating question [doohickie]
Sep 27, 2006 (7:39 pm)
I'll weigh in on this also...
I've been very carefully calculating my mileage on my 05 Elantra for the past few months. I'm typically a pretty aggressive driver — passing everyone in front of me, accelerating quickly, braking quickly, and generally having a lot of fun with the car. Under those conditions, I typically get around 28-30 MPG in mostly rural driving. I use full synthetic oil in the car, by the way.
After I received a speeding ticket in the Elantra (first one in over 20 years), I decided to slow down a bit and also see if I can get better mileage doing so. By keeping my speed at or below 62, accelerating "modestly" up to speed, braking "modestly" as well (rather than waiting until the last second and stress-testing the disk brakes), and using the cruise control as often as possible, I've been consistently getting between 30 and 34 MPG. That makes sense...nothing surprising there. But I believe that the trick to getting the most out of the (relatively) small engine is to really be careful with acceleration and deceleration. When the car is up to speed, it appears to be pretty efficient. Yet when pressed to provide a lot of torque, I think the mileage drops significantly. My own experience bears that out. When I feather the throttle more than usual, I invariably get better mileage per tank.
So I think I have the hang of working the throttle and brakes for the best efficiency. Now, I'm checking tire pressure pretty often since the weather is getting quite a bit colder in Michigan and each degree of change will affect the pressures. Having good tires that don't lose air helps a lot (I'm using B.F. Goodrich Traction T/A H tires) but nearly every tire that is filled with air (rather than nitrogen or helium) will be affected by temps. I'm going with tire pressures somewhere between Hyundai's own recommendations (30 psi) and the max cold pressures stamped in the sidewalls of the tires (42 psi). Obviously, keeping those stiff tires at lower pressures will help with ride comfort, but will adversely affect mileage. So if I'm feeling cheap, I'll jack up the pressures by a few pounds. Normally, I run around 35.
Finally, colder weather means denser air. If I remember correctly, that means higher horsepower but lower mileage since the car has to push through a "thicker" air mass. I'll back off on the performance antics and see if I can still keep the MPG figures close to summer figures, but I think that's a losing battle. I'll probably be running around 28 MPG again.
Hope that helps a bit.
#4914 of 4930 Re: MPG rating question [jvenezia]
Sep 28, 2006 (4:44 am)
FYI, basic physics states that helium, nitrogen and *air* expand and contract at the same rate with respect to temperature. In cases, volume is directly proportional to temerature. Period.
The only advantage to nitrogen is that it leaks less readily than air.
That "volume is directly proportional to temperature" part is that same law of physics that confirms your denser air bit, though. Yes, there is more oxygen for combustion per unit volume at lower temperatures. I don't think the drag of the thicker air mass has a significant effect on mileage though. Oil companies use different gas formulations at different times of the year, though, and that may affect mileage.
A couple of quick questions for you: Is your Elantra AT or MT? Also, are you basing mileage on trip computer or hand calculations?
#4915 of 4930 Re: MPG rating question [doohickie]
Sep 28, 2006 (3:30 pm)
I have an automatic 5-door GLS...no trip computer. Everything is calculated by hand. While I'm a university technology professor by trade, I don't trust computer technology all that much since I know quite a bit about it.
FYI, my statement about nearly all tires filled with air (rather than nitrogen or helium) being affected by temperatures was a bit misleading. A well-known fact about nitrogen-filled tires is that they react much more slowly to temperature changes than air due to the fact that the nitrogen contains far less moisture than air. Yes, they lose pressure much more slowly than air since rubber is less permeable to nitrogen than to air (nitrogen has larger molecules). But you're right: overall, the expansion doesn't change. What does change is the amount of expansion over time, which is lower with nitrogen and much less erratic. Is it worth up to $10 per tire to have them charged with nitrogen? It would be if you don't check your tires all that much. So I'm going to go check my tires right now since I have a long trip to make tomorrow morning.