MPG, Tyre Pressure and Wheel Size.

[KobayashiMaru 28]

What pressures are people running and what MPG's are you getting? I know these cars aren't about MPG and it's not something I've ever been bothered about. But since my brother went to PS4's on 18"s he noticed on his regular commute, which is mainly motorway and dual carriageway that mpg indicated went from 33 to 29mpg. It's only 4mpg which isn't massive and I'm putting it down to a grippier tyre(although the new PS4 is rated C so same as most tyres) but want to see what pressures people run. When I got the wheels fitted I said 35psi as that's what I've always run on 18" wheels in the past. But then there are variables like is the gauge they use accurate? Did they inflate them all the same? This is something I'll get him to check tomorrow once I know a good pressure. Wheel size could possible affect it but then the profile is less so the difference is negated. At 30mph it's barely 0.5mph.

He's said it's twitchy but what he means is it's more responsive, needs smaller steering inputs due to grippy tyres and the wheels are lighter. I noticed that instantly when driving home, even with 4 stock wheels with winters on in the back. I thought it was great. Just something he'll have to get used to and he'll be better for it.

[Church 209]

Higher grip usually comes in hand with more rolling resistance. Certainly so vs stock primacies that have less of both. Some mpg drop is to be expected from that. You didn't mention wheel/tire width, that may up grip & rolling resistance too.  Wheel diameter probably can be ignored in relation to mpg changes, unless new wheels are much heavier then stock and car is mostly driven in cities with frequent stop & go, going bigger wheels/lower tire sidewall usually reduces comfort/adds a bit to steering sharpness, not so much mpg. Also you didn't say if wheels & tires were the only changes. Biggest impact on mpg often comes from driver. For example louder exhaust for enjoyment sake may make right feet heavier to more often redline / drive longer in lower gears / floor accel & then brake again "to hear that sound, yo", instead of steady hypermiling/cruising at minimum non-lugging rpms.

[CHOSENMAN007 81]

29psi all round 18x8 on bridgestone 225/40 potenza adrenaline re002 (sticky) . As you ask what psi people are running.

Tbh im not really bothered with mpg unless im on the motorway (long journey where i just cruise to keep the mpg constant say at 34mpg ish. As you say not really a economical car. If you drive it that way on b roads its a waste of a car. 🤓

[TTR 509]

I'm on 235/40/18 Pilot Sport 4's, 28psi on the front and 30psi on the rear. Get about 35mpg-40mpg on A roads/Motorways.

[KobayashiMaru 28]

Was on stock sizes at 215 45 17's and was on winters until last week getting 34mpg. Not it's on Michelin PS4's at 225 40 18. Wheels are now lighter than stock as is the tyre compared to the winter. Guess it's just the extra width affecting it. I did say to him he's probably pushing harder on some corners without realising. Or now because it's noticeably more responsive on a straight like a motorway he's distracted and subconsciously not being as smooth with the throttle. I'll get to drive it again next week but from what I remember it was fine. Could be the front has too much toe in but geometry wouldn't be altered. Had a car once that someone put spacers only on the rear but then setup 5 degrees of toe in on the front. Turn in was nuts but on the straight you couldn't keep it in a straight line. Tbh that's extreme and I don't think it's this.

[nerdstrike 186]

A 10% increase in fuel consumption sounds a bit extreme for a slightly wider tyre, especially since the PS4s are not just wholly sticky rubber. I'd lean toward lead boot for the time being, or just traffic conditions.

[KobayashiMaru 28]

I've told him to accurately measure he needs to do the brim to brim method to really see what it's doing. Whenever I drive it, it's normally 30mpg or less, regardless of tyres. Haven't driven it without weight in since the new ones went on so I can't tell myself yet.

[Willtl 54]

Stock wheels and tyres, 35psi. 386 mile round trip left a quarter of the tank and trip computer reported this.

 

[KevinA 695]

On a long trip to sprints mainly I see 37mpg average, with a sprint/track day it still only drops to 26mpg.

18"   8.75 rims wearing 235/40/18 V105's