I was curious and began this mileage log after I replaced the front tires, I began taking the mileage between gas fill ups and learned some interesting things.
Spent $400 for a pair of new front tires on the IS. It normally takes 225/45 W rated tires, but Costco only had the higher Y rated in stock, otherwise I’d have to wait a few weeks for them to order W tires. Not wanting to risk driving on the highway nor deal with the spare, opted for the Y tires.
Honestly, doesn’t make a difference as long it’s equal or higher than the original manufacturer recommended ratings. Cost me a bit more as I also had to swap out the TPMS sensors and I find Costco is the best deal for those as well.
A real bummer as I wanted to keep the tires for at least another year as I just did the brakes on all four wheels. But the nail was in the worst spot near the edge and the side walls...just a little more to the middle and I could do a cheap plug. Cest la vie.
I do feel a slight improvement in traction and steering. The new tires definitely improve grip and I’m monitoring and so far noticed a 8% boost in gas mileage from 24 to 26 mpg. I’ll confirm after several more fill ups, but could be due to less traffic on the roads, or the nitrogen air Costco uses. But any improvement is appreciated. Annually, that just means I cut back 1 fill up for every 13 or so. So about 2 a year on my old driving habits....30 gallons or almost $75 a year.
If true...then changing tires is a decent deal.
Update 7/31/20 -- 27 mpg
Calculated that I got 27 mpg on my most recent fill up. That's pretty impressive considering I was getting 23-24 mpg before the new tires. While its about on par with what a 2007 IS250 should be getting with mostly highway miles and some city, its an improvement.
Update 8/21/20 -- 27 mpg
Its staying consistent and clocked in shy under 27 mpg for my next fill up. It's also interesting as it's about 3 weeks since my last refill and I have a 25 mile daily round-trip for work or 125 miles a week for 375 miles and came out 13.9 gallons.
Under normal conditions my weekly driving is more in the 175-200 mile range, but with COVID-19, its reduced to just commuting to/from work. That's reduced my annual mileage to about 6,500 miles a year instead of 9-10k miles in a 'normal' year. So I'll need about 240 gallons of gas or about $600 at pump prices in a year. Gas is basically nothing.
Update 7/31/20 -- 27 mpg
Calculated that I got 27 mpg on my most recent fill up. That's pretty impressive considering I was getting 23-24 mpg before the new tires. While its about on par with what a 2007 IS250 should be getting with mostly highway miles and some city, its an improvement.
Update 8/21/20 -- 27 mpg
Its staying consistent and clocked in shy under 27 mpg for my next fill up. It's also interesting as it's about 3 weeks since my last refill and I have a 25 mile daily round-trip for work or 125 miles a week for 375 miles and came out 13.9 gallons.
Under normal conditions my weekly driving is more in the 175-200 mile range, but with COVID-19, its reduced to just commuting to/from work. That's reduced my annual mileage to about 6,500 miles a year instead of 9-10k miles in a 'normal' year. So I'll need about 240 gallons of gas or about $600 at pump prices in a year. Gas is basically nothing.
Update 9/11/20 -- 26 mpg
Like clockwork, filled up after 3 weeks and hit 26 mpg. A bit less than previous fill ups and will monitor to see what could be the cause.
It's also pretty neat to see I've consistently and consecutively refilled the tank every 3 weeks. So my next fill up should be Oct 2nd.
Update 9/29/20 — 26 mpg & Boyles Law
Filled up a bit sooner as I drove on the weekend and also decided it’s better to fill up when I hit a quarter tank left. Came out to exactly 12 gallons on 312 miles. I went to check the tires and to my surprise both rear tires were measuring 43 psi when they should be closer to 37 psi. I dropped them to 40 as I wasn’t sure if my gauge was wrong, although it measured both front tires were perfect at 35 psi. I’ll check again in the morning to see if it was the hot afternoon and heavy driving that caused a bad pressure reading.
Update 10/1/20 -- Boyles Law...yes, indeed
I checked the tire pressure and yup, Boyles Law is in effect and the Front measured 32, Rear 37. This explains why on a hot day and after a long drive the tire pressure read much higher a few days prior and was front 35 and rear 43.
I reduce the rear to 40 on that day and this morning confirmed it was 37 after it was allowed to cool down overnight. However, this means the front tires are now too low and I'll top up on a Saturday morning before any heavy driving.
Update 11/24/20 -- 26 mpg
Staying steady around 26 mpg. I missed recording a previous fill up and due for another soon. It's dropping so I can only assume after 3-4 months the brand new tire benefit on mileage wanes, but then again the winter season is coming up so maybe the gas blend comes into play?
Update 12/31/20 -- 26 mpg
Did an oil change recently and will evaluate if there is any improvement in gas consumption. So far the recent refill was just shy of 26 mpg so not see any perceived benefits.
Update 1/17/21 — 27 mpg
Saw a nice improvement to 27 mpg. I’m going to monitor and it does feel like the oil change coupled with properly inflated tires has an impact on gas mileage. New tires also help and perhaps in the future when I can do all three things at once I can compare the results.
What’s impressive, this car is almost 14 years old and achieving near its originally rated gas mileage.
Update 2/5/21 — 26 mpg
Update 2/23/21 — 26 mpg
It was closer to 26.2 mpg, but I rounded it down. The built in computer showed 27 mpg which is not far off the mark so I’d say the car is calculating mpg close to true. At this point it’s consistent and steadily holding to 26 mpg.
I’m doing close to 3 weeks between fill ups so about 17 a year. I put in closer to 6,500 miles a year so I’m burning 260 gallons. Not bad.
Update 3/11/21 — 27.4 mpg
Impressive! Got one of my best mpg filling up today. Only difference was I had a recent long distance trip of about 120 miles round trip and even at higher than average speeds, this seems to improve gas mileage.
Update 4/19/21 — 24 mpg
I didn’t log a previous fill up in late March and this recent fill up was odd at how low my gas mileage. I have been sitting in traffic more often these days as things start to pick up. I don’t have much context as I didn’t start really tracking my mpg until last summer when the roads were quite empty.
Tires are properly inflated. So I’ll check and see if this was a fluke or whether traffic does bog down on gas mileage.
Update - 5/6/21 - 25.5 mpg
It’s better, but not as good as previous months. I’ll check the tires this weekend as it’s been a few weeks. I’m driving in more traffic so not clear as to why April had awful gas mileage and May is looking better? I’m also due soon for another oil change.
Update - 5/24/21 - 25 mpg
Mileage still suffering and cant figure out what's wrong? I checked the tire pressure a week prior and they were pretty good. I'll keep monitoring and my guess its the return of traffic that picked up around April time.
Only new thing I 'discovered' was something got lodged on my cabin air filter and was causing a horrible noise. The noise was sporadic for months, but got really bad the last few days and I went to investigate and discovered a thick piece of cardboard covering the filter. Not sure how that got on there and when I removed it the car seems to breathe alot easier. The A/C seems to be more efficient and I was wondering why it felt so weak these last few months.
I'll monitor to see if that has any impact on gas mileage. I doubt it, but will see on the next fill up.
Update - 6/11/21 - 24.5 mpg
Drop in mileage, but then I ran it to almost empty before filling up. So I'm guessing no matter what this car is just going to average 24-25 mpg.
I also got a recent oil change, tire rotation and checked all tires. On top of that I also need to replace the front control arm bushings so in a few weeks or so those will get updated and see if any of those impact gas mileage.
So far I'm going to rule out the cabin air filter having much impact on gas consumption. With so many variables, I cannot really correlate the actual impact.
Update 7/31/21 - 26 mpg
After the major repairs I took my first full refill and it came back a respectable 26 mpg. The bad O2 sensor and leaking valve cover gaskets contributed to a deterioration in the mileage efficiency. Kinda useful to track this for possible issues with the car.
Update 8/10/21 - 24.5 mpg
I was curious after a really bad bout of traffic where I was waiting for 3 hours I wanted to see the results in my mileage. I had half a tank left, but was shocked how much mpg I lost with some really bad traffic.
Update 8/25/21 - 25.8 mpg
An improvement from last fill up, but still below my hopes it would hit about 26.
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