I've been getting what I perceived to be less-than-optimal gas mileage lately (approximately 44mpg). I realized that the vast majority of my driving is city driving, which may be contributing to the cause. I wanted to see what the car does on the highway, which I really hadn't done yet. It dawned on me that we have a 38-mile "test track" here in Houston in the form of the I-610 Loop. Speed limit is 60mph, and after 7pm, the traffic has died down to where you'll encounter minimal obstructions.

The temperature was about 68-70F with a SSE wind of 13 mph (per the local news station). I tried to average about 60mph +/- 5mph. The Loop isn't exactly flat due to the various overpasses, but there aren't any extreme grades, with the exception of the Houston Ship Channel Bridge. I accelerated onto the freeway and reset Trip B when the speedo hit 60mph. After a full loop of 38 miles, I eaked out 58.9mpg. I don't know if this is really good or not, but more importantly, this is what I've figured out:

1. The accelerator on this thing is itchy. Pressing it a few millimeters (no exaggeration) would cause the I-FCD to plummet. Every time it fell, I'd remove my foot, resulting in a rather quick mph drop to where I would need to "tap" the speed up to 60 mph again.

2. The goal to maintaining speed and maintaining good mpg's involves pressing the accelerator just enough to prevent regeneration. The idea of driving like you have an egg under your foot is probably the best analogy.

3. My car seems to like 1800 rpm at 60mph. I had to get it up to 2200 rpm at times to get back up to speed, and below 1700 rpm, it would slow to the point where I'd have to jack it back to 2000 rpm to get it back to 1800 rpm.

In a nutshell, I'd describe the car as "tempermental," which can cause a driver without patience to become "tempermental."

I also have figured based on my early Sunday morning drive through the city streets that the car's favorite speed is a very steady 37mph. If I could drive unobstructed at 37 mph all day, I'd be pulling at least 70mpg.

I think I'd like to redo this test again, perhaps after 3,000 miles to see if breaking in the engine has any impact. Plus, the test jacked my tank average up to 46mpg

If you have any tips, suggestions, explanations, please feel free to share them. I'm still figuring this thing out.

Thank yee,
Jeff

 

Hey Jeff;

I don't have any suggestions but I would like to tell you thanks for sharing your test results with us.

Thats alot better than say 16 MPG in a SUV or Pick-Up truck.

Glad your enjoying your HCH ll.

Terry

 

Hello,
Congratulations on finding the test track!
I own a 98 VW New Beetle TDI, with 131,000 miles. I hope that
I am not quite ready for a new car.
Some thoughts/suggestions/ideas: (all involve repeating the test...)
1. Use Cruise Control at 60 mph.
2. Repeat test at 55 and 65 mph by hand/foot/accelerator!
3. Repeat tests at 55 and 65 mph using the Cruise Control.
4. Put more air in your tires. (Works for me.)

I am jealous of your already great figures.
(I don't do as well. Probably 45-48 mpg in 100,000 miles.
Biggest expense has been timing belt/water pump.)

Thanks for sharing your information

Bill

 

I did some driving tonight on some back roads. Temp was mid 30s and I used cruise at 55 mph. The realtime mpg gauge was giving me 50-55 mpg and I saw one regen bar appear very often. At one point on my drive, the battery was completely full. I don't see why the car wants regen with a full or nearly full battery. Odd.

 

My next test will be at 65mph on the same loop w/a +/- 5mph variance. I like Bill's idea of redoing 60mph on cruise control, which I'll do after the 65mph test. If I do a 55mph test, it would have to be late at night when there's even fewer folks on the road. Houston is a somewhat unforgiving town when it comes to very slow drivers.

I was also thinking about doing a lower speed set of tests at Willowbrook Mall early on a Sunday morning. I figure I have an unobstructed oval track of about 1.5-2 miles in circumference to work with. If i get there early enough, there shouldn't be anyone in the way of doing laps at 30-45mph.

Jeff

 

I just did a 65mph test on the same track, which I'm thinking about invalidating. It was 10 degrees colder with winds 10mph higher. I only pulled off 49.4mpg over the same 38 miles. The car is very sensitive in the wind. I could also distinguish the aero drag effects a little more. The car wanted to slow down much faster than at 60mph. I am a bit surprised that there was nearly a 10mpg difference between the runs.

I wonder how much it costs to rent out Texas World Speedway in College Station. I would like to do some more controlled tests without traffic to contend with. Perhaps that's a Texas hybrid gathering in the making. Hmmm...

Jeff