Finally getting interesting. MBT is the most efficient part of the timing and fuel consumption curve producing the most torque with using the least amount of fuel. All I will say is that on regular you are not in the MBT zone except at low load and rpms but knock limited which could add up to 30 percent more fuel, that is why mpg varies. Premium we get now will make a 7.5 compression motor able to reach MBT in all load and rpm zones. This should help you realize that with a 10.5 or higher compression motor your octane requirement will be higher depending on rpm and load you cruise at. Premium also changes how the ecu recognizes load based on the CA50 burn which would be fuel properties. Regular gas is still good depending on how you drive and if you can take advantage of the cost difference by using more fuel. Additives are different in premium too so you cant compare the two.

Top tier is also important because it helps keeping the octane requirement down. These statements work for both DI and normal PGM-FI motors.

 

 

https://en.wikipedia.org/wiki/Italian_tuneup

 

Been using exclusively Shell 87, and since switching over from whatever cheapest 87 was available, have seen 3-4 MPG increase overall over a period of a few months, especially on the hwy, hitting 38-40 at 75 mph with no cruise control. City gets 33-34 but takes a little hit now that I've got the AC on, 29-30

 

I traded in my 6MT for the CVT. Indeed, I can't notice any difference in power delivery from 87 to 91. But I do get slightly better fuel economy: about 40 extra kms / tank. Based on calculations, it would cost me about 400 bucks more / year to run premium given 87 would cost me just under $4k/yr total. Not worth it, so 87 it is. By the way, I love the CVT but I also miss blasting through the gears.

 

Very good discussion here. Might just pony up the extra buck or two for Shell top-tier 91 during summer whilst spinning the AC and a bit more grunt is needed, shouldn't hurt and could recover a few MPG maybe.

 

Not to mention better additives from their nitro+ formulation.

Regarding the reduced fuel economy when using 87 ... from my research it is primarily due to the ethanol content. But if I ever get something with a turbo ... then 91 here i come!

 

BTW, mine is a 2009 base Fit A/T, just over 110K miles. Got it at a Carmax with only 15k on it almost new. All I've I ever have had to do were the lost motion valve springs recall, Takata airbags, right rear power door lock actuator and have the AC charged 1 time. It was just low from the factory, kept freezing the system up. Never leaked, just needed topping up and still blows very cold. I zip tied some black plastic mesh inside the grille to keep crap from hitting the condenser and ruining it.

My only regret is I wish I'd gone for the Sport upgrade, I realized after buying it there was no cruise control, no easy aftermarket add-on. Don't know if it's possible to put it into a base Fit without replacing a lot of things just for that alone.

I've kept Pennzoil Platinum synthetic 0W-20 in it, and do Honda ATF every 30K or so. Still uses less than a pint between 8-9K oil changes at 10% on the service reminder. The chrome tailpipe finisher is still almost as clean as new, wipe a paper towel and barely see anything, so it must be fairly clean upstream and getting a nice burn. Had plugs replaced at 75k during the last valve adjustment.

I have the Torque app and what amazes me is watching fuel flow rates while driving, let off it and watch the fuel cutoff kick in and it drops to zero! It's absolutely undetectable and never a hesitation if you get back on it. During coast the A/F ratio whips up to a crazy lean number and glides right back to 14.7 very stable when you reapply throttle. Beautiful system!

 

gkitf16: I used to have a 2009 Base FIT and looked into getting Cruise Control added.

Here is the part: 2009-2013 Honda Fit Complete Cruise Control Installation Kit

I had a shop here that was going to do it for $500.00 complete but if you are an auto tech you can save some $$.

 

I just recently finished up a test with premium and for me, didn't find that it did much for mileage. The first tank was actually much worse! So it's back to 87 for me.

Oh and I did find that acceleration was a bit better, but don't think it's worth the price difference.

Can read more here on my build thread: Premium vs Regular testing.

 

Or you could always cut off a/c temporarily when you need the extra passing power

 

 

I've been running tanks of 87 and 89 and logging the different results. The only thing off is that gas prices have really been changing here in the Philly area (The price of 87 is now the price of 89, and so on) so the numbers are hardly conclusive:

87:
lowest MPG: 29.14
Highest: 35.62
Lowest Price Per Mile: .074
Highest PPM : .093

89:
lowest MPG: 31.638
Highest: 33.879
Lowest Price Per Mile: .089
Highest PPM : .091

for 87 I had an outlier trip where I was on the hwy for a long while, and a trip where i drove like a complete ass in stop and go traffic (29mpg). During my normal commute it seems even if I drive balls to the wall with limited city and a hwy commute I still see north of 31mpg. 87/89 difference sees a slight boost in MPG overall on 89, but its highly sensitive to what price i am paying at the pump to see if its worth the extra cost. Its easy to price gas at a premium over the extra 1-3 mpg over a tank vs 'saving' the $5 with 87.

 

 

I bought my '16 EX with 16k on it. I have this data collected on every tank for the last 4200 miles so far

 

are any of you guys on higher octane AND .... running a ktuner?

 

We mainly drive our Fit in the city and it rarely gets out on the freeway. We use it mostly to and from work within 8 km and around town (On our old 2008 Fit Sport (RIP) - got us roughly 19mpg to 21mpg per tank eyeballing the trip meter and 2nd kick on a full fill up.)

We just got our 2019 Fit EX CVT and from reading the previous post a high grade gas may or may not improve the mileage to make it worthwhile. We got the car at 19KM and so far the onboard Fit computer is reading 9.9L/100KM or 23.76MPG for the first 160km.

I was wondering if anyone has any city only MPG stats for newer 2015+ CVT Fits to compare? We have not tried driving with the ECO mode yet but I was thinking about switching to 91 to see if it boost our mileage on the next fill up.

 

2018 CVT Fit, with city driving only with approximately 1/2 mile to and from the store, bank, or restaurants. Not much in the way of driving and I get around 17 to 18 miles per gallon. I fully understand I would not get very good mpg with my limited driving and warm ups. Winter driving down to 16 mpg. I only use shell 93 V-Power octane for the additional cleaning additives, not for some that say it may give a slightly boost in mpg . Hope this helps.

Edit: Forgot to mention that the mileage per gallon above is with the air conditioner on as well.

 

After seeing all these users with amazing MPG it's good to know that our driving habits are causing the unusually low gas mileage. Thanks for the confirmation.

 

I'm no expert on the subject, but I believe it wont make a difference. From what I understand, 87 will burn at a certain temp, and 91 burns at a higher temp. my guess is, that 91 oct that you fill up with will mostly go out the exhaust pipe as un burnt fuel.

you can always try it out , and then report back with your findings.

there are a ton of google results on this topic, but I'll share one that I liked:
https://www.carthrottle.com/post/eng...octane-petrol/