New Tires Lowered MPG UNTIL...

New tyres need running in - but only 500kms I think.

Do you keep accurate records of your fuel use - or just the dashboard display which is only a calculation from a number of sensors, and sometimes errs considerably?

 

The type of tires is most important. Low rolling resistant tires will help get better mileage - sticky or winter tires will hurt. Run-flat tires are especially bad delivering economic good news...

 

I didn't realise that run-flats were worse - I've seen them on cars which I wasn't really considering. But it stands to reason, they're usually on prestige or sporty cars.

 

Especially heavy.

 

Tyres can and do affect fuel use.

But, if the dealer is using the same tyres at the same pressure, and gets different MPG than you, then it's likely down to one of the numerous factors that could on their own, or combined, easily make the difference you're seeing.

These include driving style, the music you're playing, your mood, wind direction, wind speed, temperature, humidity, wet or dry roads, traffic conditions, battery level at the start and end of the journey, and of course tyre pressure and types. Most of these are really hard to control for.

 

Did you check the tire pressure before and after the service visit? (When I purchased my 15 Prius, I was getting low-40s mpg while my 11 Prius regularly got low-50s.) Couldn't figure out why the new car had such poor mileage. Then I checked the tire pressure and the pressure on the new car was around 30 psi. Brought those up to 40/38 and mileage was up to high-40s/low 50s.)

 

My answer is pretty simple:
Maybe you should ASK THEM instead of speculation and guessing in a place like this.

Then......what appears to be the obvious conclusion is sometimes dead wrong.

 

As said above, probably the dealer upped the pressures (and then did a few doughnuts around the car park to bed the tyres in ).

 

Did they do an alignment? Do you know what the alignment values are on your car?

 

Tires are the most important item for MPG. Live and learn like I did. LRR, weight of tire, brand, where it is made, and PSI all have a large impact on MPG.

Recently I have discovered Pirelli LRRs do a great job for replacement tires from Sams club. Your mozzarella may vary.

To be totally safe, buy your tires online and get the OEM MIJ and pay someone to install them. Walmart will work as they normally carry those online for most cars. Tire rack for you exact tire to look for in your research.

Be careful, as where a tire is made maters.

Also the rears do not affect MPG like the front do. In a pinch, Put your new tires on the back and keep the OEMs on the front as long as you can.

42 is the ultimate answer to everything. 32 is the wrong answer. 44 is for the brave and 50 is for certified insane people.

Next is Earl!!!! Make sure you use 0W20 full synthetic earl as any thing else will drop your MPG big time.

 

Good with the tyres, but with oil, best to stick with TOYOTA's specification for your country, particularly if it's under warranty - this is Australia - it differs around the globe:

 

Good to see you alive. Wish I had an old car like me to drive around.

 

Yep - think I'm alive, was last time I checked in the mirror. You?

I noticed your Benz - bet that chews through the petrol!!!!

My Avatar is much more modern - my Dad's first car - which he bought from my Grandfather, a '49 Austin A40 Devon - mid green. This colour, but this isn't the car.

 

Those cars from the 30s and 40s had class. With seat belts, safety glass, and airbags they would be a classy ride. Usually you can retro fit most with those items. Collapsible steering wheel would be more difficult.
BTW did you see EndGame? Harry James music at the end was priceless. Had a joint replacement at VA in my foot two months ago. I seem to have survived the experience.

 

No - didn't see it (haven't seen a movie for years) - but found it I think - nice:

Though - I can't picture your Benz with seat belts, safety glass and airbags

 

Music from WWII was perfect as the world struggled to survive.

Bought the album on Amazon.

New James/

 

New tires take a mileage hit. There have been so many threads about this that it is simply a proven point. But then again, some more than others. If there is any air pressure difference in the old tires and the new tires adds to or reduce the delta.
I don't believe that there could be any "adjustment" that either the dealership or Costco could do other than pumping up the air pressure to increase gas mileage. Perhaps tracking mileage over a longer period of time and looking for trends could help. But weather, terrain, and speed play roles and that cannot be easily captured.