87 octane in a 450

[chrisschweda]

I was wondering if anyone is running 87 with there 450's and would it hurt anything long term? I went from a 04 210 with a 330 and I am now burning in a day what I would in a weekend. LOL I am averaging over 120 a day and was wondering if I could run 87?

[chrisschweda]

Wow not 1 response of if 87 can be used

[MLA]

Use what the manufacturer recommends, or the next grade higher if thats not available.

[vision]

Several folks use 87 or 89 in the 450. I personally run 93 as the performance should be slightly better. The ECM should be able to adjust timing based on the O2 sensors when lower octane gas is used and I would not anticipate engine damage, just lower performance. But I am not a mechanic.

[MLA]

Just to dispel some marketing created myths, there is no performance gain with increased octane. The performance is in the engine that requires a higher octane, not the fuel itself. 87 and 93 have about the same BTU's when compressed and ignited. This means, they expel the same amount of force to the piston when ignited. The difference is in their resistance to heat, or their volatility. Higher compression engines create higher cylinder temps during compression. Using a lower than recommended octane and the fuel charge can ignite prematurely, aka pre-ignition and spark knock. This leads to reduced engine performance and damage. Higher octane fuels resists those higher temps, until ignited on time by the ignition. Running the proper octane allows the engine to operate at its potential. Running a higher than needed octane in an engine has zero power gain. Once ignited, it has the same "boom" as lower 87 oct. The engine detects knock via the knock sensor. When knock is detected, the engine makes fuel mixture and timing adjustments. The O2 sensor is just that, a sensor that measures the post combustion oxygen levels in the exhaust. It cannot test the fuels octane level before it enters the combustion chamber. The level of O2 remaining in the exhaust, is a direct indicator of how complete the combustion event was. Higher levels of O2 indicates a not so complete combustion, meaning CO and HC gasses are exiting the exhaust. These are the 2 main pollutants, with CO being the deadly one. HC, as in Hydrocarbons, is raw un-burned fuel.

[nyryan2001]

interesting bit of data.... is that the 6.0L 450 actually has the highest compression ratio of any engine in the lineup.

so, from a logic standpoint, PV= NRT, that engine could achieve knock first all things being equal of any engine in the lineup, even before the 350 and 550. so it suggests that if ANY engine in the lineup requires higher octaine, it'd be the 450.

with that being said, we know manf ratings are slated conservatively considering the worst possible water laiden truck stop gas at a cruddy 86.589 octane.

With that said, anecdotal, I ran 87 on my 450, never once had an issue. With that said, 87 to 89 or 91 oct is like 10 cents difference, 40 gallons is $4 difference? No brainer, not worth the cheaper gas.

Another strategy is one tank at 93...use it down to 1/3 then refill with 91. etc, kinda splits the difference.

and believe me, I know fuel usage... burned 50+ gals each last 4 weekends.

[TRBenj]

87 octane in a 450

450 has a higher CR than the 409? I like to know how you determined that... Pretty sure the only differences between the 6.0L's (409/450) are the intake, cam and tune.

The rant above is mostly true in regards to octane... But it does not take into consideration that some engines can advance/retard timing in response to the octane being used. Timing changes CAN improve or detract from performance. I have it on good authority that the 450 will essentially revert to the 409 tune if lower octane fuel is used... I do believe it is safe to do so, but will not provide optimal performance.

[vortech347]

You gotta look at it this way. If you are spending $120 a weekend at $3.50/gallon that's about 35 gallons. 89 octane is typically .10 higher per gallon so that's $3.50 extra.

Is it really worth it to risk lower performance and possible engine damage over time? Remember a knock sensor retards timing "after" it has detected knock.

Gas is expensive but I wouldn't run lower than recommended to save a 5 dollar bill weekly on a 100k+ boat.

[nyryan2001]

450 has a higher CR than the 409? I like to know how you determined that... Pretty sure the only differences between the 6.0L's (409/450) are the intake, cam and tune.

I didnt determine it, PCM did. http://www.pcmengines.com/operation/

I didnt say it had higher than the 409, they do have the same as you say. But whats interesting and counterintuitive........ is that the 409/450 have the highest compression ratio.... and the 550s have the lowest...even lower than the 303/343!

So with such a low compression ratio, why do they spec 93?

[vision]

450 has a higher CR than the 409? I like to know how you determined that... Pretty sure the only differences between the 6.0L's (409/450) are the intake, cam and tune.

The rant above is mostly true in regards to octane... But it does not take into consideration that some engines can advance/retard timing in response to the octane being used. Timing changes CAN improve or detract from performance. I have it on good authority that the 450 will essentially revert to the 409 tune if lower octane fuel is used... I do believe it is safe to do so, but will not provide optimal performance.

Agreed. The ECM will adjust timing to minimize dieseling with lower octane gas which should result in decreased performance.

The difference between 87 and 91/93 at our local stations is now $0.50. Use to be 10 cents a grade and now it is 25 cents per grade increase in our area. But still not a huge amount relative to other costs.

[xrichard]

I didnt determine it, PCM did. http://www.pcmengines.com/operation/

So with such a low compression ratio, why do they spec 93?

Because it's supercharged...which changes everything wrt heat, density and pressure of the intake charge...and susceptibility to pre-ignition.

In terms of fuel required for the 450, the way I read the PCM manual, 93 is necessary for optimal performance but 87 is acceptable. The only engined specified as requiring 93 is the 550. (page 27 of the 2013 manual linked above)

[nyryan2001]

yep, I saw that, actually says damage can occur.

I ran 91 in my 550 whiel I was in Oklahoma, as 93 isnt even available at stations there. never had an issue. Now here in VA, 91 isnt available.... so I run Shell 93.

[ronskal]

The 550 is a lower compression than the normally aspirated engine because it is supercharged. Supercharging and turbo-supercharging will cause an affected compression ratio increase. This is especially true on engine that use S-charging to increase horsepower.
On some/most aircraft engines they use turbo-supercharging to provide sea-level performance at altitude and these engine do not significantly alter the compression ratio.
The fuel octane discussion MLA provided is correct from my training. All car gas is born the same and when it is final mixed at the refinery for octane they add more anti-knock additive to the 89, 91, 93 octanes than the base level added to the 87 octane. It is born with the same thermal/BTU capacity. Depending on the additives used 89, 91, 93 octanes can be considered to be BTU diluted due to these less combustive additives. Octane is merely a resistance to detonation and yes all our modern PCM engine can detect crappy gas to varying degrees. I would expect the GM LS series with all their sensors to do quite well at this whereas my PCM EX343 without CATS to be maybe somewhat less effective. I run 89 in my 343 to never have a power reduction issue induced by the ECU.

[Austintx]

So I'm curious if any of you are running octane boosters and if so, what kind? My boat will have the XR550 engine and I can imagine there may be some times when 93 octane isn't available on a lake.

I've done a bit of research and was considering having a few cans of this Torco on the boat just in case but was curious what you all do.

http://www.torcousa.com/torco_product/un_acce.html

http://torcoracefuel.net/2-docs/acce...lend-chart.pdf

[chrisschweda]

Thank you for the input I was wondering if anyone was using the 87 I have been using the 93 I have been averaging around $130 a day so almost 300 a weekend that was why I was asking. our fuel here is around 3.35 for 87 and 3.89 for 93