Having left the diesel community about the time Barth quit making coaches I have been wondering about current fuel and old engines. Is the current fuel compatible with the older engines and the new magic juice only required for newer engines. There are many older tractors, trucks, cars, boats and coaches is there any problem with the newer fuel such as lubricity, etc?

Current fuel standards for diesel road fuel require ULSD ultra low sulfur diesel fuel. The process used to remove the sulfur reduces the lubricity of the fuel compared to previous fuels. Several fuel additives are marketed to restore lubricity and reduce wear on the injection pumps.

I usually add some additive to help with lubricity and reduce algae growth in the fuel while sitting. I am not sure how much difference the additives actually make but I think they are worth using.

Just got to remembering when lead was removed from gas my engines started pinging I would add about a cup of diesel per tank and no more ping.

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a cup of diesel per tank and no more ping

Why does that happen? At first glance, it seems like 87 octane fuel is being displaced by 40 octane fuel. That would make the situation worse. Is it some additives in the diesel fuel?

happy motoring!
Matt

My reasoning was that the diesel would slow the ignition to a burn not a detonation. It seemed to work, I quit thinking about it, seldom kept cars past around 60,000 miles never had fouled plugs and eventually entered the land of engines designed for unleaded fuel and screwed up ignition systems.
Also diesel is cetane rated, 2 more carbons in the chain.

Comparing fuels is not at all simple. Octane rating is only one of several factors to consider. Octane rating is not the same as heat content, flash point, volatility, or flame front velocity.

Traditionally, octane rating is determined in a small piston engine which has variable compression. It is a measure of the fuel's tendency to detonate. Octanes are hydrocarbons with 8 carbons and 18 hydrogens. There are 18 ways to assemble 8 carbons, from straight chain to branched forms. The reference fuel is composed of so-called iso-octane, a five carbon chain with three side branches. Pure iso-octane is assigned 100 octane.

Mixtures of iso-octane and hexane (six carbon chain) are used to compare to tested fuels. Hexane detonates more easily than octane. An octane rating of 90 implies the test fuel will detonate the same as a mixture of 90% octane with 10% hexane.

Diesel fuel is more dense than gasoline (about 7 lbs per gallon compared to 6 for gasoline.) Diesel fuel contains more heat (Btu) than gasoline. (This is the main reason diesels get better mileage than gasoline engines) It also is less volatile (it evaporates more slowly.) Strangely enough, diesel fuel is lower in octane rating! (Around 25 or so)

Gasoline engines compress both fuel and air before ignition, requiring high octane to prevent detonation. Diesel fuel is injected into the hot pre-compressed air in the cylinder. Flame front velocity in the gasoline engine is entirely dependent on the fuel, while diesel flame velocity depends more on the rate of injection of the fuel into the hot air.

Diesel fuel molecules are larger and heavier than gasoline and evaporate more slowly. I suspect this is why the addition of small amounts of diesel into gasoline can reduce detonation.

I find it interesting that adding 10% ethanol to gasoline raises the octane of the mixture. However, since ethanol has about 10% less heat per gallon, the resultant mixture is less likely to detonate but it will deliver about 10% lower mileage. This is the fallacy of gasohol. Ten gallons of gasohol (containing 9 gallons of gasoline and one gallon of ethanol) will go about as far as 9 gallons of pure gasoline. I proved this a while back in my 86 Regal. I had two 40 gal fuel tanks. Filled one with gasohol and the other with straight gasoline. Ran about 30 gallons of each and the gasohol had 10% less range. Gasohol is an inferior fuel. It does not save on gasoline use. The only reasons to use it are political, not scientific.

Diesel fuel has a cetane rating which is related to ignition temperature and flame speed. Octane and cetane ratings are similar but they measure different things.

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Gasohol is an inferior fuel. It does not save on gasoline use. The only reasons to use it are political, not scientific.

An interesting statement from SteveVW. Iowa folks probably benefit more than most of the country from the sale of gasohol Today locally gasohol sells for about $2.76 and regular Gas for $3.30. We in Iowa save about 20% because gasohol is state tax funded. This benefit is because Iowa produces a lot of corn and our farmers sell it to the gasohol folks, the waste is fed to the hogs. Most other states sell gasohol at a premium price. Thank you, Senator Grassley!!

A number of small boats were built with integrated fiberglass fuel tanks. The alcohol elutes the gel and ruins the fuel system.

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Ten gallons of gasohol (containing 9 gallons of gasoline and one gallon of ethanol) will go about as far as 9 gallons of pure gasoline

Steve, would this mean that the alcohol when mixed in gasohol actually adds no heat (power) value at all???

Some slight heat value but no mileage incentive. Isn't that a waste?
Alcohol subsidies do give the farmers a break and keep some of our fuel money here at home. Farmers need all the help they can get.

Kinda screws up the corn bean crop rotation incentive, increasing fertilizer use and nitrogen runoff to the Gulf.

In a previous life I farmed, one boarder was a creek. To reduce runoff I maintained a grass border to the creek, the feedlot, 100 head over one winter, drained through pastures before reaching the creek. Presence of minnows and crayfish seemed to confirm reasonable stewardship.

Not to mention you can feed corn to people and animals. They can't eat petroleum.

Wellll, recent studies are showing plastic (a major product from petroleum) residue being insidious in water and food so maybe there's hope for being flexible as I age.

I recently read an article on the newest Dodge super car that stated the engine will produce 1040 HP using E85, which is the recommended fuel, but only 970 using 89 octane regular. I can't remember the exact name of the car but it has 85 in the name to designate it as an E85 car.