Tuning question

[cadillackman]

I was curious about what exactly is done when a tune for 87 octane is put on a Mark. I had this option on a switch-chip on my 95 & used it often back in 08 when gas was sky-high. But that chip was bought from a vendor who doesn't actually do his own tuning. I learned my lesson on that one.... Are there any longevity issues with running lower grade gas with the proper tune? I used to have an 85 Toronado that would vapor-lock like a sombeech on the cheap stuff. So naturally my main concern is the "health issues" this may or may not cause. Any & all opinions are welcome.

 

[brentalan]

I think to tune it for 87 they pull back the timing a tad. It shouldn't cause any long term issues because these cars will do their own pull-back with knock sensors if you run 87. So this just allows the computer to not pull-back as often.

Thing is, if the tune costs what, at least $200 - how long will it take you to even make up the $200 at only a few cents a gallon difference? Not to mention any "savings" you might get.

 

[cadillackman]

Well the difference between regular & premium here in Tennessee is between 40 to 50 cents per gallon. At lets say 16 gallons that's between $6.40 & 8 bucks per tank. I'm at the gas station about every week & a half. So at that rate on the low end I'd have to fill up 31.25 times (about 47 weeks) to reach the break-even point. Of course on the high end @ 50 cents difference I'd have to fill up 25 times (37.5 weeks) I guess the real difference would play out in the mileage difference. It also seems like the gap in price widens as the gas bubble grows, & shrinks accordingly. Of course it's growing now

 

[XLRVIII]

nashville premium2.91 Shell
1756 US-41 S & King St

nashville regular 2.61 Shell
1756 US-41 S & King St

thats the same 30 cents difference as here in houston

your not saving over 6.00 per tankful, it isnt 40-60 cents difference either

http://www.nashvillegasprices.com/index.aspx?fuel=A

the power you lose, will cause you to
1. press the gas further to get up to speed {killling economy)
2. press the gas pedal for a longer period of time to get up to speed (killing economy)

the BEST way to get better mileage is to get a 93 octane tune, and enjoy the
benefits of having more power..which IS economy, so long as you dont run around WOT all the time enjoying the new found power.

 

[XLRVIII]

and the "tennessee average price is 3 cents lower than the national average"

 

[kustomizingkid]

Premium fuel ftw... most people don't understand that more power is better... all the time for everything

 

[cadillackman]

Here's one from my side of town.
Shell in antioch, http://www.nashvillegasprices.com/Shell_Gas_Stations/Antioch/39382/index.aspx
.36 cent difference
Shell on West End, http://www.nashvillegasprices.com/Shell_Gas_Stations/Nashville_-_West/54094/index.aspx
.36 cent difference.
From my above guestimation I was thinking about Home Depot's gas station, which ass rapes you with a low posted price on regular, just to look @ the pump & see that premium is usually .40 cents more. You're right, my base numbers were high. I should have came correct with real numbers. The site only shows regular for these stations. But i will be heading over there a little later & will gladly snap a cell-pic just so it doesn't seem like i'm trying to BS on the .40 cents. Wal marts have the same pricing structure.
There are gas stations around here that have a .30 difference ,but there are just as many that are more than that # & there seems to be no rhyme or reason
I see your point on the difference in power, are you saying that it's a complete wash?
I'll do the same math @ .30 & .36, @.30 X 16 gallons=$4.8 /$200=41.66 fillups
@.36 X 16=$5.76/$200=34.7 fillups, so that's 62.5 weeks low, & 52.05 weeks high.
So how bad will the lost efficiency eat into the gains in price difference? I was debating the addition of this option as 1 of 3 tunes assuming that I can get them put into an xcal2 for an un-ridiculous price.

 

[XLRVIII]

The site only shows regular for these stations.

there is a premium fuel tab on that site, the have all three grades and diesel.

you can sign up and report you local gas prices too.

i wouldnt bother w/economy tune...i have spent alot of time working on a economy tune...the power loss sucks

 

[driller]

I'll do the same math @ .30 & .36, @.30 X 16 gallons=$4.8 /$200=41.66 fillups
@.36 X 16=$5.76/$200=34.7 fillups, so that's 62.5 weeks low, & 52.05 weeks high.

At least you're doing the math.

I love arguing with people who want to trade their Mark VIII for an econobox. The math usually opens their eyes. For most people, the difference is only a few dollars per week in actual fuel costs and the accrued costs of the 'economical' car more than offsets any savings in fuel. Even still, once you ask if you want to ride in a Mark VIII every day for X dollars or ride in a {fill in the blank} for Y dollars per day, the difference in fuel costs suddenly looses it's appeal.

Back on topic, your math assumes you'll get the same mileage. Arguments have been made that may not actually be the case. I would bet money it certainly wouldn't be better mileage with regular fuel. I wouldn't know, since I only buy premium fuel for my cars.

Interestingly enough, I had a premium fuel tune made for my '06 Harley F150 daily driver and get better mileage than before - more than enough to offset the cost of premium.

 

[CobraStar_LS8]

I get 30mpg drivin' 55-60mph constantly and 24mpg around stop lights after stop lights...I ain't complainin'

 

[Infarc]

Or you could just do what I did... put on a water/meth system that lets me run 87 octane fuel. When I am cruising on the highway there's no difference. Once I get my foot into it a little ways (anything over a third of a pedal), the w/m jumps the octane up to about 97 and I get the benefit of the additional timing in my tune.

Per tank....

16 gallons at 2.78 a gallon = $44.48 44.48/24 mpg*16 gallons = .116 cent per mile to run premium

16 gallons at 2.49 a gallon = $39.84 39.84/24 mpg*16 gallons = .104 cent per mile to run regular

Over the course of a year, putting about 10K miles on the car that ends up being about a 120 dollar a year difference.

 

[cadillackman]

I think that's the math I was looking for.

I'm not looking to permanantly use cheap gas, I just want the option for the summer months in case we're looking at a repeat of 2008. but if the loss in efficiency is so great that it kills any gains in savings, it's likely not even worth it, which seems to be the general consensus.
The water meth idea sounds like a good way around power loss, but don't you have to use windshield cleaner in that?

 

[Infarc]

I think that's the math I was looking for.

I'm not looking to permanantly use cheap gas, I just want the option for the summer months in case we're looking at a repeat of 2008. but if the loss in efficiency is so great that it kills any gains in savings, it's likely not even worth it, which seems to be the general consensus.
The water meth idea sounds like a good way around power loss, but don't you have to use windshield cleaner in that?

I use a 50/50 mix of water and methanol. I can point you to all the NACA work that shows why that is the ideal mix, and exactly why and how it affects fuel and engine performance.

Just be aware that a good W/M kit is going to cost you about 300 bucks, so you are looking at 3 years to recoup your investment if you are thinking of it as a economy thing. Also it is entirely possible that my average MPG went down by about 1 by switching to 87 and if it drops by as much as 2 mpg then the whole math thing goes out the window. Personally I am using it because of the anti-detonation factor that it adds to fuel so it is really more of a safety device to me. I really didn't expect to see a gain at all when on motor but when we got finished tuning it (you have to pull back about 10% of your fuel when it is injecting) I picked up 40 horsepower, on 87 octane gas. And I have the dyno sheets to prove that. My track times went from 14.4s on 93 octane to 13.9s on 87.

If you are looking for something that will let you preserve an aggressive timing curve while running the cheap gas, AND having a safer time of it, then it's your thing. If you are going to try to justify it penny per penny then at best you are looking at a couple of years before it pays for itself.