Community Forums

RattlenRam · 09-13-2007, 05:38 PM

Is the 93 octane fuel better to use than the 87 octane. Will it give you more power, and beter fuel milage, or is the extra cost not worth it. I have the GM 8.1. If this topic has been covered befor sorry for the repete

RattlenRam · 09-13-2007, 05:38 PM

Is the 93 octane fuel better to use than the 87 octane. Will it give you more power, and beter fuel milage, or is the extra cost not worth it. I have the GM 8.1. If this topic has been covered befor sorry for the repete

Oemtech · 09-13-2007, 06:14 PM

Yes it is better assuming that your engine is tuned to take advantage of it. But, the 8.1 is not tuned that way. So, the short answer is stay with 87 and save your money.

Full-Timers · 09-13-2007, 06:16 PM

The higher the octane the harder it is to burn so less mileage.

RattlenRam · 09-13-2007, 06:45 PM

It sounds to me like I better stay with the fuel grade I have ben useing and stop trying to improve on something that aint broke.

Paul Heuvelhorst · 09-13-2007, 08:23 PM

RattlenRam,
Consumer research has demonstrated over and over, whatever octane the manufacturer of the vehicle recommends, you would be foolish to use any octane other than that.

When you use a higher octane than recommended, you are just throwing money into the gas tank that has no additional benefit.

John-D · 09-14-2007, 04:42 AM

Unlike the one person I'd not say the higher octane will give reduced miles per gallon.. Though it WILL give less miles per dollar.

The standard engine computer is programmed to use 87 in most areas. and even a bit lower in some areas (Altidute seems to "Improve" octane ratings so where as 87 is needed here in Michigan, Get up in the mountains perhaps 85 will do) and has quite a bit of adjustment. If you fill 'er up with higher octane you may feel better, but it won't. If 89 or 9x makes it verifably run better... YOU NEED SERVICE.

RustyJC · 09-14-2007, 04:56 AM

Whether or not an engine can take advantage of the higher octane fuel depends on the control strategy utilized by the manufacturer. For instance, my 2007 BMW K1200GT motorcycle uses a relatively high output engine (152 BHP from ~70 cubic inches) for which BMW specifies 91 octane fuel (minimum) and utilizes knock (detonation) sensors to protect the engine and as an input to set ignition timing. This serves two purposes:

1. It protects the engine should, let's say, an 87 octane fuel be used by sensing knock caused by the lower octane and retarding ignition timing until the knock falls below acceptable thresholds. This retarded timing, however, has a negative effect on brake specific fuel consumption, power output and exhaust temperatures.

2. Should 93 octane fuel be used, it will allow ignition timing to be advanced automatically by the ECU up to the knock threshold - which is now higher than it would be with the 91 octane minimum fuel recommendation. This additional timing advance will give improved brake specific fuel consumption and power output.

If, however, an engine control system cannot take advantage of the higher octane fuel as described above, there's no benefit in using the higher octane fuel other than improved detonation (knock) margin and possibly higher detergent dosing in the premium fuel.

Rusty

FrontRangeRVer · 09-14-2007, 06:01 AM

Our "regular" grade Unleaded up here is 85 octane......We use the "medium" grade 87 octane

I have heard that you are wasting your money if you use the "premium" 91 octane (93 elsewhere) as you will see no benefits except lighter in your wallet.

RustyJC · 09-14-2007, 06:07 AM

Right. Higher altitude reduces the compression pressure (and, therefore, the peak firing pressure) of an engine due to the lower air density and barometric pressure. Because of this, octane requirements at higher altitudes are reduced accordingly. That's why 91 octane is frequently the highest octane fuel found in high altitude regions.

Rusty

DriVer · 09-14-2007, 07:07 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by RattlenRam:
Is the 93 octane fuel better to use than the 87 octane. </div></BLOCKQUOTE>Short answer is "NO" however Ultrapower will adapt for use with Hi-Octaine fuels however I would be dishonest if I were to tell you that 93 Octaine made any difference at all.

All Workhorse owners should be aware that 87 Octaine is the "minimum" they should consider using when fueling their vehicles. The 8.1L engine is very content using 87 Octaine gasoline.

"007" · 09-15-2007, 02:22 AM

If you are looking for improvement in gas milege a Ultra Power upgrade of your ECM will work it did for me.

Ultra Power

Ultra Power #2

DonavonP · 09-16-2007, 03:40 PM

If a gasoline's octane is raised by adding ethanol then using the higher octane gasoline will actually lower your miles per gallon as it has less btu's. In some states, the higher octane gasoline with ethanol is sold for .05 gallon less but your better buy is the no ethanol gasoline because of the increase in mileage.

A 100% 87 octane gasoline should get you about 5% better mileage than a higher octane ethanol blend of 10%.

RustyJC · 09-17-2007, 04:10 AM

Just about all the gasoline in our EPA non-attainment area has up to 10% ethanol added as an oxygenate. And, yes, mileage dropped when the ethanol came in due to the lower BTU/gallon of ethanol as compared to gasoline.

Rusty