Tire change. Am I crazy?

[JSH]

No, you aren't crazy. As others have stated mileage often drops a lot with new tires. Not only is the first 1/32 of a tire generally a gripper compound but the more tread, the more tread squirm, the more heat generated which equals lower fuel economy.

It also seems you when oversized - which as redpoint said will increase speedometer error and understate both speed and miles driven. This will be even greater if your last set of tires were smaller than stock.

Then there is the change in gearing. Larger tires = lower RPM which could put the engine out of the efficient powerband and make it lug more at lower highway speeds.

Then there is the fact that MPG is a poor unit to measure fuel economy because it is not linear. The higher the base MPG the less fuel saved by each additional mpg.

Driving 15,000 miles a year:
30 mpg = 500 gallons per year
60 mpg = 250 gallons per year (Saving 250 gallons)
90 mpg = 167 gallons per year (Saving 83 gallons)
120 mpg = 125 gallons per year (Saving 42 gallons)

[redpoint5]

Originally Posted by JSH

Then there is the fact that MPG is a poor unit to measure fuel economy because it is not linear. The higher the base MPG the less fuel saved by each additional mpg.

Of course we've discussed this several times, but I don't think the general public is aware of diminishing returns or how this measure of fuel economy isn't intuitive to understand.

Much more important to figure out how to get a 15 MPG vehicle to get 20 MPG than to figure out how to get a 50 MPG vehicle to get 55. I basically don't care if the Prius ever gets better fuel economy because the difference between $0.06 per mile and $0.055 per mile isn't that important to me.

[freebeard]

"Tire change. Am I crazy?"

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Betteridge's law of headlines is an adage that states: "Any headline that ends in a question mark can be answered by the word no." It is named after Ian Betteridge, a British technology journalist who wrote about it in 2009, although the principle is much older. Wikipedia

[JSH]

Originally Posted by redpoint5

Of course we've discussed this several times, but I don't think the general public is aware of diminishing returns or how this measure of fuel economy isn't intuitive to understand.

Much more important to figure out how to get a 15 MPG vehicle to get 20 MPG than to figure out how to get a 50 MPG vehicle to get 55. I basically don't care if the Prius ever gets better fuel economy because the difference between $0.06 per mile and $0.055 per mile isn't that important to me.

Same here. Driving an efficient car also makes most ecomods one could do money losers.

The Pilot Sport tires I put on the Bolt dropped the summer efficiency from 4.7 miles / kWh to 4.1 miles / kWh. That is a 13% drop in efficiency which in my experience is about average when going from crappy LRR tires to a good performance all-season.

So do I care? NO. It is the difference between $0.015 / mile and $0.017 / mile. 2 tenths of a cent per mile or $2 a month. That is a very small price to pay for a safer car.

[Phase]

well i drive 45,000 miles a year average. car is 4 years old and has over 180000 miles on it. not to mention west coast prices are insane for gas. mpg doesnt matter as much in places like texas or alabama

a 5 mpg boost in my car equals to 50-60 extra miles of range, which can make a huge difference in making it to a cheaper gas station to fill up

for example, driving from portland to boise on one tank of gas can let me make it to a costco, and save 50 cents to a dollar per gallon of gas, which is a lot of money when completely filling up. the gas stations in between boise and portland are close to a dollar more than the boise costco

5 mpg boost is also saving an extra gallon of gas per fill up which is almost 5 dollars, when that could be used towards lunch. or on a multi state trip with several tanks filled up, that savings could equal a nice dinner at a restaurant saved or a super dirt cheap hotel room or added day of vacation

[JSH]

Originally Posted by Phase

well i drive 45,000 miles a year average.

Which is more than 3x average yearly mileage (13,500). The more you drive the more fuel economy matters. Are you a courier, regional salesman or something?

Commercial drivers that drive a lot of miles care a LOT about fuel economy - at least the big fleets do. They get excited about saving 0.1 mpg. Owner-Operators - not so much. They are the ones buying the cowboy trucks with a big engine, old fashion non-aero design, and LOTS of chrome.

Originally Posted by Phase

not to mention west coast prices are insane for gas. mpg doesnt matter as much in places like texas or alabama

87 octane is $3.79 a gallon at the Hillsboro Costco and $3.89 at the Fred Meyer. Diesel is still pricey though - $4.89 at Freddy's.

[Ecky]

When I had my Insight, I found the difference in fuel economy between my summers (Potenza RE92) and winters (Nokian Nordman) was negligible. Tire size was identical. I typically ran the winters at 48PSI. There was a general decline in fuel economy, but it tracked outside temperature (which could be >80F between summer and winter), and there were no sudden changes around tire change time.

The Nordmans did a good enough job to drag the car through <6 inches of snow - I would only ever get stuck when I high centered the car. I could get good traction in ice slick enough I couldn't stand on it - I recall one time being unable to fully get up a hill, so I turned the car off and put it in 1st/ebrake, and got out, only to fall on my ass and slide down to the bottom of the hill. I couldn't get back up it to the car, parked halfway up the hill, without a rope.

~

I have no need for winter tires where I live now, but on the topic of tires: On my MX-5, I'm thinking of swapping my Pilot Sports out for something much lower RR once they're finished. Outside of road trips I only drive the car maybe once a week, for pleasure, but premium is equivalent to ~$7.75US per gallon here (diesel is closer to $4.75 - I should have gotten a diesel) and over the last year and a half I've gotten most of the "go sideways" out of my system. I'm ready to get back into mostly eco-driving.

My current tires are 1.7% oversized and I make sure to calculate that in when I record a tank here.

I've personally never observed a steep decline in fuel economy with new tires. I wonder if the effect is more pronounced with wider tires?

[Phase]

Originally Posted by JSH

Which is more than 3x average yearly mileage (13,500). The more you drive the more fuel economy matters. Are you a courier, regional salesman or something?

Commercial drivers that drive a lot of miles care a LOT about fuel economy - at least the big fleets do. They get excited about saving 0.1 mpg. Owner-Operators - not so much. They are the ones buying the cowboy trucks with a big engine, old fashion non-aero design, and LOTS of chrome.



87 octane is $3.79 a gallon at the Hillsboro Costco and $3.89 at the Fred Meyer. Diesel is still pricey though - $4.89 at Freddy's.

I just drive a lot for vacation and boredom. Oregon is a beautiful but huge state. Hundreds and hundreds of miles just to do a crater lake day trip or a trip to southern Oregon to gold pan. Plus driving to mount hood and back 3 times a week in winter helps add almost 1000 miles a week to the car. Filming snowboarding pays YouTube income and it’s good exercise and therapy.

Biggest mile adder is doing road trips from Oregon down to Arizona probably every other month tk see friends and get some sunshine. Or my yearly road trip to Florida and back to see east coast family. And then in winter I usually drive to Colorado twice plus ski trips to Utah and Idaho and New Mexico and so on. I constantly drive spring for fun since this car is so great on gas and I like seeing new sites. Plus making YouTube videos when traveling around helps with income

[JSH]

Originally Posted by Phase

I just drive a lot for vacation and boredom. Oregon is a beautiful but huge state. Hundreds and hundreds of miles just to do a crater lake day trip or a trip to southern Oregon to gold pan. Plus driving to mount hood and back 3 times a week in winter helps add almost 1000 miles a week to the car. Filming snowboarding pays YouTube income and it’s good exercise and therapy.

Well that explains a lot. Crater Lake is a 500 mile / 8 hour roundtrip drive. You must really like to drive. I've been to Crater Lake 5 times now but never without an overnight stay somewhere.

Originally Posted by Phase

Biggest mile adder is doing road trips from Oregon down to Arizona probably every other month tk see friends and get some sunshine. Or my yearly road trip to Florida and back to see east coast family. And then in winter I usually drive to Colorado twice plus ski trips to Utah and Idaho and New Mexico and so on. I constantly drive spring for fun since this car is so great on gas and I like seeing new sites. Plus making YouTube videos when traveling around helps with income

Oregon to Florida? That is 6,000 miles / 6 days round trip drive at least. I'm taking it you just like to drive because after making cross-country drives I can't see how driving would be cheaper than flying unless you are sleeping in the car.

For me about 500 miles is my driving limit unless I am either in the campervan doing an extended trip or on the motorcycle. Anything farther and I'm flying there and back for a few hundred bucks. A direct 2 1/2 hour flight to Phoenix is $250 roundtrip. We were supposed to fly down last month for a fly and ride motorcycle trip last month but my mom got sick. Now we have her dog for the winter so that will limit travel until spring. $50 a night to board a dog adds up quick.

[redpoint5]

East coast driving is hardcore, and this is coming from someone who is hardcore. I prefer to drive, but my limit is anything east of the Rockies. I can drive 24 hours straight, but anything further I'm better off flying (and I hate flying).

I once flew to Kauai for a week vacation and packed all my clothes and laptop and sunscreen, etc in a backpack, and all my SCUBA equipment (minus tank and weight belt) in my carry-on. Sure, I'm not transporting a kayak or surfboard or anything else huge, but I can get creative when taking advantage of the "included" luggage rules. If I could drive to Hawaii, I'd still fly even though I hate it.