Mitch Kahn knows that I cover more than just tech these days…

I just caught your podcast on tips to get better gas mileage and was surprised that there was no mention of TIRES – yes TIRES. Since I’ve become somewhat of an expert on this, I thought it was worth a detailed email.

Most noticeably missing from the list was TIRE PRESSURE – it should have been tops!

He rolls on:

Tires should be properly inflated at all times. Insufficient air pressure will not only reduce your mileage but also cause your tires to wear out prematurely. Keeping air pressure higher will yield better mileage albeit with a harder ride (don’t over-inflate or you’ll also wear out your tires prematurely).

In addition to tire pressure, make sure your wheels are balanced and aligned.

Not as well known is that tire tread can also make a big difference. Rolling resistance is the keyword here.

My car supposedly has some kind of tire pressure monitor, but I believe they improved it in subsequent years (somehow). So long as the dealership maintains the 5k mile checkup records, I’m not too worried.

Mitch has a story, however:

I bought a Toyota Prius hybrid in April 2004. I now have 114,000+ miles on it (yep, that’s 30k/year). The vehicle (which is now my favorite of all the cars I’ve owned) came with Goodyear Integrity’s. Utilizing some restraint in driving techniques I was able to squeeze out 55 mpg in normal everyday driving.

At around 45,000 miles I decided to replace the tires. None of the Prius blogs had much information on replacement tires because the model was so new (2004 was the first year of the 2nd generation Prius and I had one of the first delivered). I was also probably one of the first to wear out the OEM tires.

I opted for a set of Michelins at COSTCO (best place to get tires for many reasons). My mileage immediately dropped to 45. I upped the tire pressure to try to compensate but that yielded only a marginal improvement.

After struggling through 30,000 miles on that set of tires I had a conversation with the manager of the tire department about it and he offered to replace them (free of charge) with a set of special order “green” tires from Michelin. They did no better. I didn’t feel like pushing my luck with COSTCO and decided to just live with the situation and wait until I needed to replace tires again. This was Dec 2006.

At some point last summer (2007) while browsing the tire store at COSTCO again, I noticed that Michelin changed their tread pattern to match the Goodyear Integritys that came with the Prius. I wondered about it but couldn’t justify replacing the tires again. I certainly wasn’t going to ask for a SECOND set of free tires.

Fast forward a few months. Last week one of my tires picked up a nail and by the time I noticed it was too late to save it. This was just the excuse I needed to replace ALL the tires. I bought the updated Michelins and voila – the mileage is now back up to 55 mpg. In fact the other day driving with a tail wind (at 65 mph), I averaged over 58 mpg on a trip from Miami to West Palm Beach. Word must have gotten back to Michelin about the problem with the previous tread pattern.

In closing, the Prius is an extremely kool car and it’s technological bells and whistles truly make it a geek’s delight. Properly maintained and intelligently driven it CAN get it’s advertised mileage. How many people do you know who can go 550 miles on $30 worth of gas? If every car delivered 55 mpg, the Saudi’s would be left to drink their oil.

• Tips to Properly Maintain your Vehicle