Run Dry or Not!

This has probably already been discussed, but I couldn't find it. For years I have used only Unleaded Premium Gasoline in my outboard and other small engines - weed eaters, lawn mower, etc. I always leave gasoline in the carbs - even over the winter. They always start right up.<br /><br />As a matter of fact, I had a small crack in one "plastic" bowl on my 1994 Johnson 88HP special (Mix oil with gas) last summer. I replaced both carb bowls with the newer metal versions. However, I noticed no gum or varnish in the carbs after 11 years of operation. They looked almost brand new.<br /><br />A friend of mine INSISTS on disconnecting the gas line and running the motor until it dies after each trip. However, I believe this procedure would run one or more cylinders dry (without gas/oil) before the engine died and possibly cause more engine wear and failures.<br /><br />However, neither of us seem to have any problems. BTW - he does agree with me on burning only Unleaded Premium in the outboards.<br /><br />OK, so here's the question....what's the RIGHT procedure? Or is there a concensus of opinion among you experts?

Re: Run Dry or Not!

The engines will run just fine on plain unleaded 87 octane.<br /><br />Engines with more than one carburetor. Running the engine out of fuel will result in having the upper carburetors run dry first if for no other reason, gravity. The engine continues to run after a fashion (so to speak) on the remaining carburetors.<br /><br />This allows at least one aluminum piston ro be running up and down a steel cylinder wall with improper or no lubrication.... really not a good idea.

Re: Run Dry or Not!

Yup. What Joe said. . . exactly.

Re: Run Dry or Not!

It is common here to tell boaters to use regular gas in their outboards and premium is a waste of money. But the fact of the matter is that OMC recommends premium. It's right in the owners manual. It specifically states that use of permium fuel is preferred over regular and will help to keep the motor cleaner. <br /><br />So why deny that OMC wants boaters to use premium in its outboard motors? By denying this basic fact, you are depriving you fellow boats the protection afforded by using premium in the form of reduced deposits and wear.<br /><br />So, if you have an OMC outboard, grab the owners manual and follow the advice from the people who made it and have to honor the warrantee.

Re: Run Dry or Not!

Mark.<br /><br /> I have a 1995 John, 130 hp, on page 8 of my operation & maintenance manual.( Fuel ) use any regular unleaded,regular leaded,or premium unleaded automotive gasoline that has not been extended with alcohol.<br /><br /> Use of alcohol extended fuels is acceptable ONLY if alcohol contents does not exceed:<br /><br /> 10% ethanol by volume<br /> 5% methanol with 5% consolvents by volume.<br /><br /> Minimum Octane,<br /> <br /> Inside the U.S........87 (R+M)/2AKI<br /> Outside the US........90 RON. This should clear the things for everyone.

Re: Run Dry or Not!

My manual says the same as JC's. Maybe Mark is refering to the newer stuff.

Re: Run Dry or Not!

Mark.<br /><br />Please tell us which manual for which engine states that premium fuel is preferred and keeps the engine cleaner.<br /><br />I have seen similar statements, but only for 4 stroke engines.

Re: Run Dry or Not!

Fact is about 15 or so years ago premium gas had carbon dispersants as additives and regular unleaded didn't. Nowdays all grades of gas have it. No need to run premium.

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The older manuals DID say that. It is not necesary now, for the reasons Walker cited.

Re: Run Dry or Not!

"Premium" gas today means higher octane, not cleaner or better or more powerful. Higher octane gas ignites and burns at a higher temperature than lower octane gas. It is desirable in engines designed to operate at higher temperatures. High compression, high output engines may require high octane gas to prevent pre-detonation in the combustion chamber.<br />Some engines do not run well on Premium gas. My 1975 4HP Evinrude and my weedeater don't. Premium gas retards the burn rate and makes them run rough. Some engines do not run well on Regular gas. My 1988 Honda car is one. At 240,000 miles the motor suffers from pre-detonation and run-on unless I burn premium. Some engines don't care one way or the other. My 1989 Chevy pickup runs well on anything. Premium, kerosene, maple syrup, it doesn't seem to matter to Big Red.<br />Use whatever the motor runs well on. Rough running motors lack power and wear out. If the motor runs equally well on Regular or Premium you will get no benefits in performace or longevity by using Premium.

Re: Run Dry or Not!

Well this is the recommendation from a 1975 manual<br /><br /> ENGINE FUEL AND LUBRICANT<br /><br />TYPE OF GASLOINE: Use premium or regular leaded gasoline with the following minimum octane number.<br /><br /> RESEARCH OCTANE NUMBER. 94 <br /> Most commonly used in the past<br /><br /> PUMP POSTED OCTANE NO. 89 <br /> Number posted on gasoline pumps since September 1973.<br /><br />At that time 89 octane was premium, I've experimented on a couple of occasions with higher octanes' such as 91 etc. The end result was poorer performance especially at higher rpms. After some research I found the reason was that higher octane fuels burn off too quickly resulting in less efficient combustion. Of course this was just my personal experience

Re: Run Dry or Not!

The last line spoken by Rhett Butler as portrayed by Clark Gable in the classic movie Gone With The Wind was what?

Re: Run Dry or Not!

I'll be back?

Re: Run Dry or Not!

The only time you would need to be concerned about running the carbs out is during annual winterizing.It is always a good idea to drain the fuel out of the "older" engines, most all of which have vents in the carbs. Running the engine to where it stalls is not a problem if you are spraying the fogging oil in the carbs when you do it. If you do not run gas out of the carbs, the light gas vapors will evaporate, leaving the gum and residue of the gas in the bottom of the bowl during long time storage. Once variable ratio oiling was introduced this concept is no longer a good idea-with the gas line disconnected, the oil side of the pump will fill the bowls with oil (only) and it will not start in the spring. You can manually drain the carbs in this case. Newer engines with fuel injection are closed systems and do not suffer from evaporation-just put stabilizer in the tank. You can also put some fogging oil in the fuel water separator and run for a few minutes.

Re: Run Dry or Not!

Regarding the Alcohol extenders; in NJ the fuel does not have alcohol. In NY it does, but not enough to exceed the specs by OMC.<br /><br />Walker is right, since 1995 the Environmental Protection Agency (EPA), through the Clean Air Act, mandates that cleaners be added to all fuel. None the less, according to my Exxon Engineer source, Premium still has more cleaners than regular. You are not just paying for octane. <br /><br /> <br />And from our friends at Shell:<br /><br />"Today we estimate that 60% of fuels sold in the US are at or near the minimum level of detergency allowed by law. However years of vehicle testing by Shell has shown that the EPA minimum level of detergency is not sufficient to prevent deposit build-up in some cars. We have measured significant deposit build-up in certain vehicles in as little as 5000 miles. Testing has further shown that some of those vehicles can experience cold start drivability problems as a result.<br /><br /> The image shows Intake Valves after a 5,000 mile Shell test comparing Shell V-Power to a discount brand premium gasoline.<br /><br /> <br /><br />(Note: this is regular cheapo brand vs Shell Premium. Quite the difference! What cheapo brand do you run?) <br /> <br />Shell regular and mid-grade gasolines contain more than twice the amount of detergents required by the EPA. This level of protection helps prevent the future build-up of carbon deposits on your vehicle’s intake valves or fuel injectors. However, if you use discount gasolines, you may already have intake valve or fuel injector deposits, which may need to be cleaned up. That is where Shell V-Power® comes in." <br /><br />Regarding their premium brand fuel:<br /><br />" Shell V-Power® premium gasoline can clean up deposits on intake valves and fuel injectors left behind by low detergent gasolines. That’s because it contains more than five times the amount of cleaning agents required by government standards."<br /><br />So, yes, my dear Scarlett, Premium fuel does have more cleaners than regular or mid grade. Depending on manufacturer, up to 5 times as much. <br /><br />Also the lube oil added to the burn mix creates more residue to build up. Cheap fuel with oil is not my first choice to run in my 2 cycle!!! Clean burning TCW3 does not mean Zero residue, it just means less buildup than burning straight 30 weight.<br /><br />I know that some of you guys burn hundreds of gallons a year. The cost of premium adds up. But for boaters like myself who burn about 100 gallons a year, the cost of premium over regular is only an additional $20 a season to get the higher level of protection. Compare that to fuel additives at the parts store to treat 100 gallons will cost more than the price of buying the premium at the pump. Today my local station has regular at 2.09 and premium at 2.29.<br /><br />bold accents added by your truely.<br /> <br />BTW, why is this picture of Peter Jennings on the Exxon Mobil web page?<br /><br /> <br /><br />Alright, so it's not really him, but the resemblance is striking.

Re: Run Dry or Not!

Mark42, I beg to offer an alternative interpretation to the intake valve pictures. <br /><br />The valve on the left has a dirty appearance even on the mating surface where the valve face and valve seat touch. This is not caused by dirty fuel or lack of detergent. <br /><br />This is cause by an improperly bedded-in valve or a worn, leaky valve. This area does not get "sooted" up unless something is wrong mechanically. The valve on the right shows the normal bright line. Without "backflow" this whole valve will look better than the bad valve no matter which fuel or additive is present. <br /><br />So I think the left valves' dirtier appearance is a result of an intake valve that is leaking compression and/or combustion gases and this is enough to alter the stain pattern you see.<br /><br />As for fuel and gumming up, most of the problem is water in the fuel. This is what turns gummy,orange slime into varnish deposits. My experience is like Capt George.

Re: Run Dry or Not!

H,<br /><br />Just for arguments sake, is it possable that the valve on the left as buildup because buildup on the valve seat caused it to not seat well? Sort of the snowball effect?<br /><br />Also gotta remember, it's advertising. So ya gotta take it with a grain of salt. <br /><br />Their claim of higher levels of cleaner is most likely true.<br /><br />I doubt that ANY gasoline manufacturer decided to increase their levels of cleaners when the EPA mandated cleaners in fuel. They normally put more cleaners in premium than regular. My guess is that the EPA spec is so low as to be marginally effective.

Re: Run Dry or Not!

Capt George... My initial response stands.

Re: Run Dry or Not!

I tend to agree with Joe and others, 87 octane seems to work just fine, that and running the correct plugs. Joe I think that last line went something like "Frankly my dear Scarlet I just don't give a damn"

Re: Run Dry or Not!

If we want to nit picky, which this thread is getting good at, it was, "Frankly, my dear, I don't give a damn."<br /><br />I don't think a 1975 manual or Shell's research on automotive 4 stroke engines are relevant to Capt. George's question.<br /><br />This is what Joe believes, and I agree:<br /><br />There is no known benefit in 2005 to running premium fuel in a 1994 88 SPL. 87 octane unleaded will do everything 93 will do, and for less cost.<br /><br />Running a multicarb engine dry involves risk of avoidable wear and failure.