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FAQ: Substitute Car Diesel for Boat Diesel


Can I Substitute Car Diesel for Boat Diesel Fuel?

Original Message:
Can I Substitute Car Diesel for Boat Diesel Fuel?

Decided to pump the diesel fuel out of the bottom of my tank and see what kind of crud shows up. If it is bad, I will pump the whole tank but there is no diesel fuel sold at my winter haul out place. Nearest pump is four boating hours south.
My question is...can I put in 10-gal Car Diesel fuel till I get down river and fill up at the boat yard? Is it the same stuff but with the marine color agent? Don't contact the Diesel Police, please!
Thanks for any info.
Capt Al, #55, C34 _/) "Kindred Spirit

Below are all the responses to this question without any identifying names….to protect the innocent!

RE: Can I Substitute Car Diesel for Boat Diesel Fuel?
Hi Capt. Al,
The only difference in the fuels are the color additive and road use tax. The color is to let the "Diesel Police" (DMV) know if you are using non-tax paid fuel on the highways. In North Carolina we have a 42.5 cents per gallon road use tax. There is no reason you should not use the fuel in your boat. There is a hefty fine for going the other way.

Actually you are better off buying your diesel at a truck stop, it is probably cleaner fuel.
A trick to drain the tank: disconnect the fuel line at the tank and replace it with about 20 feet of cheap 1/4 inch plastic tubing, then pull your speedometer
paddlewheel and drop the tubing through the hole. You can siphon the fuel from outside the boat, no mess or smell in the cabin.

There is noting illegal or bad about running car diesel in your boat. It's the same stuff. They just add dye to show that taxes have been properly paid. You just cannot run marine diesel in your car. It won't hurt your car, but it's illegal due to taxing.

Yes, it is the same. Scurrilous, unethical and otherwise delirious people have been known to use D2 from truck stops exclusively for many years and in several boats. Of course, I fully discourage you from slighting the Federal Authorities their full measure of tax and fees on the marine approved and dyed variety.

Yes its the same stuff however the oil companies put additives into the over the road diesel during the winter month if you are in a colder climate, hence it is a touch better than the marine diesel.

Go to your local truck stop and get some of whatever they're selling. Usually, in the winter they sell #1 diesel or a blend of #1 & #2 cause it's thinner and won't get goopy in cold weather. Summer time they usually sell #2 diesel. Stove oil used for heating is usually #1 diesel - with no use tax :). Didn't they bag the fuel tax for boats or remove the requirement for colored fuel?

Capt Al
I used to run up to my local gas station and fill up a five gallon jug for the boat all the time (much cheaper that way).

I believe they are the same. If so, you can put car fuel in the boat, but not boat fuel in the car (red diesel means no road taxes were paid).

For years I used to fill up 6-Gallon Diesel Jerry Cans at the Local Truck Stop and fill my boat. Never had a problem, works great. In fact sometimes it’s better because there is a high turnover and typically very clean fuel. (p.s. in the past, this way, you could even bypass the silly boat diesel fuel tax(red fuel?) they had imposed....I believe that has been repealed by the us congress)

Charlie : Unless I've got my wires crossed, red dyed marine diesel is free of the big highway taxes.  From what I've experienced the cost of "gas station" diesel is usually 30-50 cents a gallon higher than at a municipal marina. In fact it's illegal to sell the red diesel to other than a boat and some marinas will not allow you to fill a container - only put it in your boat's fuel tank. Usually if I need a fillup I go to where the work boats go. I also put on about 300hrs a year.   Ron  APACHE  #788

I don't know about other sates, but, in California, number 2 diesel is the same no matter what pump you get it from. I have never used fuel from a fuel dock. I always bring a 5-gal jerry can to top off the tank. Seems easier to me.

The dye in diesel fuel is to show that road tax has been paid on it. This doesn't apply to boats so car fuel is fine.

I'm going to alert the authorities. The Coast Guard will no doubt set up a floating blockade, board & seize your boat, then sell it at a contraband auction.
Anyone want to bid on a highly upgraded Catalina 34?

We have used gas station diesel some before, with no ill effects. I believe this summer on Lake Michigan, with water down 9 inches from last years extremely low water, we will be either driving to the gas station, or walking to the gas dock, as the gas dock only has 5 feet of water and I have a fin keel.

You can use...Boat Diesel, Car Diesel, Truck Diesel, Tractor Diesel, Heck you can even go to McDonald's and use their French Fry Oil.... But those darn Left Over fries get stuck in the Injectors.. :-)A couple of kids in a VW car did just that. They toured the US by going to drive-ins, getting the used cooking oil.. I think they called their car .. "Veggie Wagon" or something like that. In other words .. there is no restriction on diesel..

It is the same fuel. I have been filling cans at the local gas station. It is a lot cheaper than at the marina. The closet marina that sells diesel in my area is 12 miles.

I only use car/truck diesel and have no access to "boat" fuel.

Same/same as far as I know. I put stabilizer in it as I only go through about a tank a year.

Important: The opinions expressed here are those of the individual contributors to this page, and not those of the Catalina 34 National Association or Catalina Yachts, Inc. Additionally, this material has not been reviewed by Catalina Yachts, Inc. for technical accuracy. This page's maintainer cannot guarantee the accuracy of this information or the desirability of suggested modifications or upgrades. Please obtain assistance from a competent marine mechanic or boatyard prior to making any significant modifications to your vessel.   


Last modified by Phil Imhof, Wednesday, August 11, 2004 . Copyright © 2001 by Catalina 34 International Association.  All rights reserved.