Holy **** first tank of premium
04-29-2013, 08:17 AM
#91
04-29-2013, 08:52 AM
#92
Senior Member
I have never used premium on a long term basis. I did put 2 tanks in back to back just to satisfy my curiosity a little while back. Here is my honest evaluation:
1) The truck did have smoother power delivery on premium (Shell 91 octane)
2) Shifts felt a little crisper...maybe
3) Would the truck tow better on premium? Yes probably
4) At almost $0.20 more a liter in Ontario a full tank of premium cost me an extra $19.60 (98 liter tank)
5) I saw little to no difference in mileage with no change in driving style...and if there was a difference it didn't come close to offsetting the increased cost of the fuel.
Premium is nice for the better power delivery and for towing, but for my money I'll stick with 87 octane. In real world driving premium is just not worth it for me.
1) The truck did have smoother power delivery on premium (Shell 91 octane)
2) Shifts felt a little crisper...maybe
3) Would the truck tow better on premium? Yes probably
4) At almost $0.20 more a liter in Ontario a full tank of premium cost me an extra $19.60 (98 liter tank)
5) I saw little to no difference in mileage with no change in driving style...and if there was a difference it didn't come close to offsetting the increased cost of the fuel.
Premium is nice for the better power delivery and for towing, but for my money I'll stick with 87 octane. In real world driving premium is just not worth it for me.
04-29-2013, 09:10 AM
#93
One Bad MoFoMoCo Owner
Glad we could find some common ground. The above is exactly correct. If MBT timing was 32, then there would be no gain from increasing octane. If MBT timing was, say, 34, and it was knock-limited to 32 on 87, then you would have to advance the timing to 34 on 93 to gain anything at all.
The test that made me rethink all I thought I knew about octane was in Car Craft, probably 20 years ago. They did an octane test on a low compression Mopar V8. They changed octane several times and retuned for max power. When they switched to leaded race gas (~110 octane), they actually found that MBT timing was about 8 deg lower than with pump gas, plus it made more power at this lower timing advance. So, even though the race fuel was capable of running much more advance than pump, it actually made more power at lower timing advance. The theory is that the race fuel was more highly refined and, thus, a narrower range of hydrocarbons, resulting in a faster flame front, and less MBT timing required. Improved combustion chamber shapes will have this same effect, though I am assuming that the 5.0 and EB both have very good chambers (that has been the trend).
And no, I am not Mike from 5 Star.
The test that made me rethink all I thought I knew about octane was in Car Craft, probably 20 years ago. They did an octane test on a low compression Mopar V8. They changed octane several times and retuned for max power. When they switched to leaded race gas (~110 octane), they actually found that MBT timing was about 8 deg lower than with pump gas, plus it made more power at this lower timing advance. So, even though the race fuel was capable of running much more advance than pump, it actually made more power at lower timing advance. The theory is that the race fuel was more highly refined and, thus, a narrower range of hydrocarbons, resulting in a faster flame front, and less MBT timing required. Improved combustion chamber shapes will have this same effect, though I am assuming that the 5.0 and EB both have very good chambers (that has been the trend).
And no, I am not Mike from 5 Star.
That said, the differences in power, as I have stated, would be slight, but still noticeable in acceleration, under load, and at high speeds that simulate high loads due to wind resistance.
My point is our trucks and many other engines today have the capability to adjust to higher octane fuels, it's not just knock sensors pulling back the timing, because engines are more sophisticated than every with multiple mapping options built in these days. Do they go as far as a tuner would, no.
No one will save money by getting better mileage, because you can't make up the now 30 cent price difference. Hell, it's unlikely you could make up a ten cent price difference. If the price difference is justified by the individual owner's enjoyment of his truck, that's all that matters. The worst that will happen is the extra additives keep his engine cleaner...
04-29-2013, 02:05 PM
#94
Senior Member
FWIW it takes about 60 hp to push your truck 80 mph.
Last edited by engineermike; 04-29-2013 at 02:10 PM.
04-29-2013, 02:12 PM
#95
Meek One
All this bickering makes one think twice before posting a simple, "wow, try premium fuel" now, doesn't it? I get where you're coming from and I appreciate your post.
04-29-2013, 02:49 PM
#96
04-29-2013, 06:25 PM
#98
The questions about fuel types and mpg crop up all the time here. Its amazing that so few every search for a topic before posting. The premium debate has been beaten into the ground and we continue to get experts giving their two cents on the question. Next another E85 post will show up asking if its worth putting into our trucks and again ton of replies......
04-29-2013, 07:40 PM
#99
