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Regular Unleaded Gas (stock) vs Premium Unleaded Gas (tuned)

11K views 53 replies 16 participants last post by  focusedaddiction 
#1 ·
I was just curious how a car performs differently once tuned to run on premium grade gas? Here in California, our grade goes from 87, to 89, to 91. 91 being the premium. I drive a 2.0 Duratec ATX. So, is switching what type of gas your car takes part of a tune if you want it to be? Does it net you any gains over regular unleaded? What's the difference in performance and power and is it worth it to tune your car to these specifications? Or could you see similar gains with a tune just keeping it on regular unleaded?
 
#3 ·
Ok, sounds good. So then it basically works like this: 87 < 89 < 91? So obviously 91 would be the best gas to use for playing hardball? Good to know.

Personally, I only make it out maybe once a week every weekend. So I'd probably do the race tune once a week (keeping only 1/4 or less of premium gas in it so it runs out by the time I want to put 87 in) and then for the rest of the week I'd probably go back to the 87 tune to save money on gas. I don't know how realistic that would be, but I'd be open to try it. I don't know, it may be a hassle, but I don't care. I want every advantage for speed and power on race day, but for every other day of the week, I want to the advantage of the cheapest gas.



FYI, I'm right on the cusp of committing to fully modding my car. So it shouldn't be too much longer. Most likely after smog is finished (next week). Then I'll order the tune and everything else. Those damn ricers wont know what hit them! [hihi]
 
#4 ·
Yes you can do a 87 and still get the driveability and then have a 91 tune for playing

I charge 399.00 and 20.00 for shipping and you get a full Custom Tune and FREE tune updates as you add more mods which no one else does so you wouldnt be charged extra for both the 87 and 91 tune and they both would be a custom tune not a generic tune like most others sell and I dont charge to look over your datalog

Tom
 
#5 ·
I'll be coming to you here before too long. I'm almost ready.



But can you explain to me what exactly the difference is (and what you get) between an 87 tune and a 91 tune? I'm sure a lot of other things factor into it, but specifically tuning the car to run on 91 vs 87, what exactly is the difference?
 
#8 ·
Yeah, but gas where I'm at is up to like $4.60+ for premium. Regular is still around $4.13. We'll see how these prices hold out and depending on that, I'll make up my mind about the 91 tune. Otherwise, I'll just get high performance tune while still maintaining 87 grade gas.
 
#13 ·
in the uk we got 95 as regular and 99 as premium i find it mad how ur cars run on 87. man that must be crap/powerless.
 
#21 ·
Does adding Octane Booster to your car do anything beneficial? So what if I get a premium octain tune and then add a can of octane booster?

Simple answer, no.


If you look into how the Octane system works you'll find that most boosters claim to raise by "points". What they don't tell you on the bottles is that 1 Octane is equivalent to 10 points. SO a bottle that claims to raise Octane by 8 points would raise 89 to 89.8, not 97 Octane.

It's my opinion that if you truly need something to raise the fuels Octane rating above that of pump fuel, you should be able to afford the costs of quality race fuel, else the mods you've done are all in vein. Also there can be relatively simple tricks to ward off spark knock W/O the use of high buck fuels. Simple things like indexing your spark plugs might help, running shorter gaps or lower heat range plugs.
I have indexed my plugs for a while now and it might just be placebo but it kinda seems that it helps some. I point the open end towards the center point of the exhaust valves.
 
#23 ·
No. Unless your car is made to run on the higher octane. If you put 91 octane in an svt it will get better fuel mileage than with 87( Not that I would put 87 in my svt). This is because the svt is designed to run on the 91. Google octane if you really want to know more.
 
#24 ·
I'm talking about getting a tune for it. Are you going to get better gas mileage with an 87 tune, or are you going to get better gas mileage with a 91 tune? In other words, I'll be getting a tune either way, but which tune will get me better gas mileage? 87 or 91?
 
#25 ·
I believe it depends on the kind of tune you want, you can tune more for performance or economy. 91 burns a little smoother than 87.

Does the ECU in the focus not adjust to octane ratings like other cars? Example, my V6 accord will adjust to different octanes and advance or retard timing to compensate, but switching from one to the other you need to go about 500 miles on the certain octane before the computer recalibrates for the octane. Running 91 instead of 87 will get rid of pinging and get me slightly better milage although on 87 I can average 35mpg on the freeway (about 1 mpg better with 91). A honda engineer has said running 91 instead of 87 will give you a 10hp bump in the accord as well. All this without a tune.

Thanks for bearing with me, trying to expand the knowledge of my vehicles.
 
#27 ·
I believe those benefits are usually only for engines that have VCT and even further variable lift also. As the Focus does not have that (the SVT has the VCT on only one cam). I think you also tend to have more knock sensors and other electronics to determine detonation and then the best timing and fuel map combo to use.

Please correct me if I am wrong.

also 1 MPG increase, for at minimums 10 cents per gallon for a 1MPG increase? looks like around me its about 15 cents average more for 87 (our 91 octane up here at 4,700 feet). $1.95 more for 13 miles distance... that's not cost effective, as over two fill ups, i would go 26 more miles for $3.90... at this moment I can get 1 gallon of regular for less than $3.90 and go further than 26 miles on it.
 
#28 ·
Thanks for the info and clearing up my confusion, I kinda assumed that most cars now could sense the higher octane and adjust. Most of the V6 accord guys don't get 91 for the extra mpg, more to prevent knock, advance the timing for the extra hp and for the boosted/built guys it really helps alot. I've only ran 91 once to clean out my injectors and noticed a slight better response but no power bump from what I could tell (Ass dyno).

Edit: Also stand alone ECU's are very rare/ non-existent for the accord so the octane bump along with the timing advance is beneficial for us.
 
#31 ·
It all comes down to money. If you want the extra performance, you need premium fuel. If you can only afford 87 octane, or refuse to buy premium for what ever reason, just leave the stock calibration. Heck my father/mother in law still believe gas is gas and all the octane grades are a scam. Would anyone believe Mustang 5.0/GT-500 owners using 87 octane?...............I do because I have witnessed it!. Of course it does not help that most dealers recommend 87 octane(regualar) gas for everything except diesel trucks.
 
#34 ·
^^^ no but you most likely will not see any gain...
 
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