Interview with a hypermiler

Yesterday, we returned from our week-long vacation in Boston for the Williams syndrome conference. On the way there, we stopped overnight to visit Seth's sister and her family. As we were driving to her place, late, late at night (I had the brilliant idea that driving at night would be easier with the boys), I was trying to keep Seth from nodding off and decided to interview him about hypermiling. You're welcome in advance.

Well, Seth, thanks for sitting down for this interview with me.

I don’t have a choice. I’m driving and you are talking.

Yes, well, thanks anyway. Let’s get down to business, shall we? The good folks who read my blog want to know about hypermiling.

You mean all 10 of them.

Eleven. Eleven people read my blog.

Your mom, your sister, my sister, my other sister, my other other sister, and my sister-in-law.  That’s six people.

And my dad.

Ok, so seven people read your blog.

Yes, well, they all want to know about hypermiling.

Are you sure?

Fairly. So, to begin, how do you define hypermiling?

Hypermiling is beating the EPA rating (or whoever it is that makes the mileage standards), the manufacturer’s MPG ratings. If you’re in excess of their ratings, you’re hypermiling.

What got you interested in hypermiling?

I wanted a car that could get to work on less than a gallon of fuel and back again on less than a gallon (49 miles each way). A guy I worked with, Mark, was hypermiling in his old vehicles, and he introduced me to hypermiling. He said he thought I could be competitive because I know what I’m doing around cars. It gets addictive.

What was your first step toward hypermiling?

Learning what it was and what other people are doing – basic techniques. What has to be refined specifically to what you’re driving.

What was the first car you tried hypermiling in?

VW Jetta, a diesel. It went OK – I got it to 53 MPGs. (When Stacia drove it, she averaged about 40 MPGs.) It’s not as easy with an automatic because it’s very limited in what it can do and wastes a lot of power and energy in the torque converter. You can’t select or hold gears. It also doesn’t coast properly.

Where did you go from there?

I purchased a VW Golf TDI for my daily commute and also tried hypermiling the Ford F-150 truck.

How did it go with the truck?

I made it up to 18.5 MPGs, which was better than the 14 it normally got.

For some reason, thinking about hypermiling a truck makes me laugh. Anyway, how did it go with the Golf?

Pretty well. You learn a lot as you go. I’ve been averaging 69/70 MPG lately, but it should be in the low 70s at this point in the year. It started at mid 50s when I first got it.

What modifications have you made to the Golf to increase fuel efficiency?

I put some grill blockers on it – they prevent air from going through the engine bay and route it around the car. That reduces drag. I change the amount of the grill that’s blocked based on the time of year – in the summer, you need more air flowing through; in the winter, less.

I removed the passenger side mirror (it’s not illegal—the driver’s side is the only one required). It takes it out of the airstream and reduces drag.

I put an aluminum skid plate under the front of the car, again to reduce drag.

I deleted the day-time running lights.

I changed all the other lights to LEDs.

I use low-rolling-resistance tires (48 psi).

I lowered the suspension 1.5 inches.

I advanced the timing mechanically. I advanced the fuel-injection time and also in the software. This changes the curve that it runs on. The faster your engine runs, the more it has to advance the fuel it sprays into the cylinders, in relation to where the piston is [holds up hands to show me—I remind him he’s driving]. So it ignites at the proper moment and burns most efficiently.

I got rid of the EGR (exhaust gas recirculation) – in a diesel it stops up the intake manifold with gunk. Without the EGR, the intake manifold stays clean so it doesn’t restrict airflow.

I added a block heater and an oil pan heater. They preheat the car so that it runs more efficiently at the start up and keeps the engine warm. It’s also good as a maintenance item to reduce the thermal transients across the block in heating and cooling cycles. It keeps everything warm so that it’s all closer to the temperature it needs to be to operate. A diesel is a heat-compression ignition and when the engine does not have heat, it does not run well, and the glow plugs have to stay on, which wastes power from the battery, which then has to be made up by charging from the alternator, which takes fuel.  It presents a counter-torque to your engine.  [My eyes start to glaze over. Did I mention this was taking place at two in the morning?]

I put a taller fifth gear in it, which went from a .756 to a .658. This changes the ratio of your engine RPMs to output RPMs that drive the wheels. But then the transmission went out on it, and I had to rebuild it again and put a sixth speed in it.

I put a freer-flowing exhaust on it—a high-flow catalytic converter and a 2.5-inch straight pipe.

I also indexed down the windshield wipers a bit to get them out of the airstream.

Which one of the modifications you’ve made to your car made the biggest difference?

It’s difficult to say because while I was modifying the car, I was also refining my driving techniques. But probably the transmission and tires and timing and injection quantity (which I also modified in the software) and a higher temperature thermal set.

That’s more than one thing.

Yes, well, the question was invalid to begin with.

What are the best driving techniques you’ve found for hypermiling?

Planning your routes and knowing your stops. Conserving momentum is key. You burn fuel to get up to speed, and any time you hit the brakes you waste fuel, and you have to burn more fuel to get back up to speed. Any time you lose momentum, you’re forced to regain it.

You have to learn where, when, and how to coast (shifting to neutral) which maximizes your conservation of energy. Sometimes I just push the clutch in, if I can accelerate going downhill. Other times, I use the engine to slow the car down – engine braking in the Golf uses zero fuel consumption – it burns less fuel than engine idling (coasting out of gear in neutral). You have to figure out how to coast and maximize your returns going through stop lights in town. You have to time your stop lights so that you don’t actually have to stop or losing as much momentum as possible. If you’re coming up to a light and you’re not going to make it, you need to start stopping much earlier so that when you hit the light, it’s green and you can keep on going. You need to learn to watch for cross traffic so you can know whether the light is going to change. If I’m coming up on a green light and know I’m not going to make it, I’ll start slowing down so that it takes longer to get to the light and, hopefully, by the time I do get there, the light is green again and I can keep on going. When I slow for a light, I use engine braking and mechanical brakes.

The AC is a huge drag on the system, so I don’t use it. The heater isn’t quite as bad as the AC but I don’t use it, either. The only air that moves through the car is from the natural ventilation that is pushed through the car from the cowel, which forces it through the vents.

Rolling down the windows increases the drag a lot, so I don’t roll down the windows.

Don’t speed. Speed kills fuel economy because drag increases exponentially with speed, which means you have to burn more fuel to overcome the added resistance against the vehicle. Drive the speed limit. Optimal fuel economy is generally at the point where you’re at the top gear going the lowest speed you can maintain without lugging. In my car, the optimal speed with the current transmission is about 50. The lower RPM you’re running, the less internal friction you have to overcome.

Ride the ridges in the rain. When you look at the road, you’ll notice there are dips in it from where most people drive. When it rains, the water collects in those dips and your tires are forced to push the water out of the way, creating drag. So drive on the parts of the road that are higher. Also when it rains, you want to make sure you your tires are highly inflated – the higher the inflation pressure, the greater your speed you can travel before beginning to hydroplane because you’re increasing your wet traction (but decrease some of your dry traction – which it a good trade-off).

Drafting is a possibility, as long as you do it safely by staying far enough away from a larger vehicle that you’re not putting yourself or anyone else in any danger. There are small gains to be made there.

When you’re going up a hill, you’ll get better mileage if you can maintain the same average speed by going up slower and coming down faster than if you try to maintain the same speed throughout a hill.

What about weight? Does adding more weight decrease your fuel mileage?

In stop-and-go situations, yes. But once you’re up to speed, it’s not a factor. Weight is more of a factor when stopping and starting, but it’s really not a huge factor. Definitely not as big of a deal as you might think.

If you don’t use the AC or roll down the windows in summer, it must get pretty hot in your car as you drive during the afternoon hours. How do you deal with that?

I tinted the windows to minimize interior heating. I got a white dash cover. I got a Stacoolvest.

What about using the radio?

It draws power, so it reduces fuel economy. Any of your electrical parts will affect fuel consumption. I use the radio when I need it to keep me awake while I’m driving, but otherwise, I don’t use it.

How much have you saved with your hypermiling ways?

Just with the Golf, according to my calculations, I’ve saved somewhere around $4,500 since I bought it in 2008.

Would you say you’re addicted to hypermiling?

I suppose. Only in that one vehicle, though. It’s become a hobby for the Golf, just to see what’s possible. Although I use some basic techniques in anything I drive.

Yes, could you please speed up a little now? It’s late and I want to get to where we’re going.

Any websites that you recommend for more information on hypermiling?

Ecomodder.com is decent.

Any other insights?

Keep up with routine maintenance on your car to keep it running optimally. And keep track of your mileage – it’s a good gauge to let you know if something’s going on with your car that needs to be fixed. I keep track of mine on fuelly.com and ecomodder.com and also in the TDIClub forum.

Would you say you’re the best hypermiler ever?

What? No. Believe it or not, I’m not as dedicated as some people. Some people take it to extremes.

What does your wife think about all of this?

She’s fully supportive and appreciates all the money I save that she can spend elsewhere.

Actually, I think you’re crazy in the head.

Yes, but you love me anyway.

True. Well, thanks for the talk. Are we there yet? And . . . could you go a little faster?