Has anybody documented the MPG improvement (if any) from lowering? I found a couple of threads discussing this but no data. I am going to install the Eibach Pro Kit Springs tomorrow (0.8" rear, 1.2" front) and will document my findings in this thread. If anyone else has any data, please post it in this thread also. EDIT/Update: Since lowering I am seeing a 5% increase in MPG (see page 2 for more details).
I would check if prius has enough room for caster and camber play. As long as you able to set caster and camber back to stock, you should not loose any mpg. in order to get better mpg with lowered car you would need to travel at the speeds that Prius cant reach. btw, what is the top speed on this baby? c
Without strict controls on variables I doubt you can accurately measure the difference. In theory it should help but that is about as close are you are likely to get.
In theory, the mileage would go up because of the improved aerodynamics. Mine would likely go down, because it would be more fun to drive faster.
Hi f8l! I'm planning to do 17s with lowering kit. What's your estimated mpg hit due to the bigger and heavier tire and wheel? How much are the eibachs? Suggestions on wheel package or tire brand and size. Thanks! Archie
Not exactly. Camber will definitely become more negative when lowered, which may or may not be fixable depending if it's in the front or rear. The more negative your camber is, however, the better mileage you'll theoretically get because there's less tire being dragged on the road. But camber isn't even that important. It's toe (and caster) that you ought to be concerned about. The drag coefficient is not significantly changed when lowering since it doesn't produce much of a downward force. There's also roughly the same amount of lift even when lowered. In the end, you can expect the same mileage. However, as a couple have pointed out, it's a lot more fun to drive, so you'll probably lose a couple mpgs flooring it through corners every now and then.
Hey, Archie! If you get a lightweight wheel and a good LRR tire you maybe only drop a couple mpg. This is assuming you have good 15" LRR tires now. Wheels are totally up to you. As long as you stick with something under 20 lbs you should be ok. Because my car is red I have been jonesin for the MSR 045s. I'll be keeping my 17" Centerlines as they only weigh 15lbs and look good enough. My next 17" tire will be the 215/45/17 Michelin Primacy MXM4. It appears to be the most efficient (LRR), long lasting (500 treadwear), highest performing tire in that size and it is priced well. The Ecopia EP100 looks good too but at $195/tire I cannot justify the crazy price. The Eibach Pro-Kit is $209 at TireRack.com.
I lost 2.5MPG on my round trip commute (66 miles) with my 17" wheels (my wheel and tire specs are in my signature). I got the Eibach's from AutoAnything for $200 with a 10% off coupon and free shipping. I am hoping to get a little MPG back with the lowering.
You may have heard about all the trees falling down in the south due to the bad weather. It's not over yet, and I'm considering using that method to lower my Prius from the top rather than underneath. If it happens, I'll let you know the MPG effects.
Update (Initial Results): since lowering I have gained the 2.5MPG back. Now, this may be coincidence and I will collect more data but my commute was giving me consistent MPG BEFORE I upsized my wheels (53.5MPG) and consistently lower MPG AFTER I upsized my wheels (51MPG). In other words, I believe the initial improved MPG results are real and not just a fluke. I also found an interesting article from Eibach documenting MPG improvements from lowering. It can be viewed here: http://images.autoanything.com/images/info/eibach/eibach_pro_kit_mpg_test.pdf
I don't trust Eibach's claim and here's why. The company needs an unpaid, independent, disinterested third-party to perform the test. "As Eibach proved" doesn't cut it for me. Ideally a third party would perform a test and tell Eibach, in which case Eibach can say "these are the results that can be achieved!..." This is the essence of the advertisements we see. For a company to make their own scientific claim is bold, however. My industry is biotech (R&D) and I've worked with our sales and marketing staff to determine the sensitivity/effectiveness of our products. We would never make such a bold product claim based on an in-house test result.
Update: Noticeable increase in MPG continues. Since lowering I have gained 2.5MPG on my commute, which is what I had lost from adding 17" x 7" wheels. I lowered the car primarily for appearance but the increased MPG is a bonus.
