#1 recommendation for highway driving in cold weather: pump up your tires 750 miles in 35F @70mph = 43.3mpg (actual) (45.6mpg displayed) Just did a round-trip of 750 miles, 95% of which was highway at 70mph (the other 5% was short trips around 40-60mph, so they actually hurt the overall mileage). Temps ranged from 30-40F, altitude went from sea level to almost 2000ft and back again (with a 2nd climb of 1000ft in the middle). I recently changed my tire pressure to 42/40psi front/back - similar runs (in slightly colder temps) were as low as 39mpg actual with the tires at 37/35 and almost the same grill blocking. After factoring out the temperature difference, I think the additional 5psi gave back about 2.5-3mpg highway. So, the #1 recommendation I have for cold temps: pump up your tires. You will feel the bumps more, but on reasonably good pavement you won't notice (in fact, I think firmer tires may be a bit quieter). Just remember to let some air out when temps warm up again.
I didn't notice much if any of a difference from psi of 40, so i just run mine around 34 i'm not saying others wont, but the extra wear on the suspension parts/tires and me doesn't seem worth the little if any mpg effect. I'm not trying to say it didn't help you. But i'm wondering if alot of the people complaining about rattles, and how their car rides has something to do with overinflated tires?
You know, I didn't notice any rattling when driving home from the dealer 2 months ago. The dealer inflated the tires to about 32/32 so they were extra cushy/comfortable. Now at 38/35 the comfort is just okay. I'm mainly worried about suspension as you are.
I wouldn't worry about the suspension if you are just driving on pavement. If you rally it on dirt roads, like I've done with my genII, then worry. Otherwise its a Toyota and they are built to last so inflate away my friends.
I think rattles can be an issue even with the stock PSI, but softer tires do soak up bumps more. I'm not worried about the suspension, shouldn't be an issue unless your roads really suck. I should have titled the thread "#1 recommendation for highway driving in cold temps" - I don't think the difference is quite as noticable at lower speeds, although it is still there to some extent.
The thing that really changed my MPG is setting ECO mode and the heater to 16C/61F (the minimum before the "LO" setting) since I keep the coat on (overall commute trip 25mins). It looks like cold, but it is bearable and you see a true benefit in fuel consumption. Otherwise I would keep it at 22C/72F. The engine does not turn on so often during stops at traffic lights and overall fuel consumption has improved considerably (0,5L/100km-5mpg less on average). Also warm-up is shorter. On longer trip outside of town, this likely does not help - I agree. Wheels are pumped nominally and I get regularly about 4,3L/100km-55mpg on the evening trip (less traffic) and 5,3L/100km-44mpg on the morning one (more traffic). This with temperatures around 0C/32F.
I can also agree. I've tried various techniques to obtain better mileage during the winter. Pumped up my tires to 41 front and 40 back. I'm mainly driving short trips <10 mil. which also hurts my mileage. However, as I do go on longer trips my mileage for that tank creeps up. So, I do know I CAN get the better mileage, it's just that the short trips and long warm-up times hurts the MPG's.
Over-inflating means to EXCEED the maximum pressure listed on the wall of the tire. Modern tires will retain their shape surprisingly well up to that point. 42/40 is under the maximum of 44. .
This point has come up so many times in the last half-decade that very determined testing has been done. You can find the results showing improved handling, reduced stopping distances, extended tire life and even tire wear and improved mileage throughout PriusChat, CleanMPG, GreenHybrid and I'm sure many other locations.
I'm using snow tires, so even if there were a marginal change to the tire qualities due to the added (not "over") pressure, the snow tires still make a huge gigantic enormous difference over the OEM's in crud. The snow tires also cost me about 2mpg vs the stock tires (on clear roads), so if I used the OEM's with the higher pressures I would expect to get 45.5mpg or possibly 46mpg in the same temps at the same speeds - that gets a lot closer to the 48mpg EPA highway, which should be easy to beat on a regular basis as soon as temps get over 40F or so. (they were the past day or so, and my displayed mpg is at 51.4 after more than 100 miles of "around town" driving)
This would carry more weight if you could link to a few of the key threads - but I'm not surprised at what you're saying, manufacturers almost always use less-than-optimum tire pressures in order to increase ride comfort.
I have been to two different dealers for service. Both dealers have increased the tire pressure to the max shown on the tire side walls 44 PSI. Yet the door plate shows 36 front and 33 back for recommended inflation. I see about 3 or 4 MPG better with the higher tire pressures. I keep bringing the tire press back to half way between the dealer pressures and the door label pressures. I am concerned about the wheels with the higher tire pressures. Some manufacturers have had problems with wheel fractures from over inflation. Do the dealers have some sort of tech notes or instruction to increase the tire pressure beyond the door labels? Barn
