Good day,

My GLS Accent has a 1.6 MPI automatic engine that I bought new in 2008 has about 150,000 Kilometers on it. With basic service (not from dealers), petro 91 octane fuel and synthetic amsoil fluid changes this car is running better than when I bought it. Now I'm planning to use Seafoam every where! Its difficult to get info in Canada regarding throttle body sensors, but I think this car has only a map/iat sensor and more in the air intake throttle body.

My question is do you think using Seafoam Spray as recommended through the air intake throttle body would harm or improve any sensors in question that send data to the ecm unit to regulate fuel combustion and emissions

thanks Jan

  • Not sure about the Seafoam, but your engine does not need 91 octane gasoline, and using it will not improve performance in any way. Stick to 87 octane and save yourself some $$. Sep 6, 2017 at 20:46

1 Answer 1


Seafoam can be very helpful to an engine, but not specifically to the map and iat sensors. Those are not affected much by carbon deposits, so cleaning them won't really help. See this link for a more detailed discussion.

I once destroyed an engine by spraying too much Seafoam all at once through the air intake. The liquid cannot be compressed like the fuel/air mixture, and I damaged the piston rings. I suggest you pour it into the fuel tank instead. The cleaning effect will actually be better, it will just take more time as you drive the car. I follow the instructions from Seafoam in this video. Don't forget to floor the car, 80-120 km/hr., six times in a row on an open highway!

After researching the ingrediants in Seafoam, I concluded it is best suited for 2-cycle, marine engines. Marvel Mystery Oil is better for a four-cycle car, especially if you follow with a tankful of Berryman's B12 Chemtool (or an equal mixture of acetone-xylene-isopropanol). If Marvel Mystery Oil is unavailable in your country, automatic transmission fluid is practically the same thing. Start with a 3x concentration of MMO, which amounts to 1.2 oz. per gallon of petrol.

Also, use Marvel Mystery Oil (or ATF) in the crankcase oil. Engines much above 90k KM almost always seem to have sticky piston rings & valves. I get better idle, acceleration, and less oil consumption when I use Marvel Mystery Oil in the crankcase for 1,000 KM, then change the oil again. If you like Amsoil products, I have used the Engine and Transmission Flush before an oil change to enhance cleaning.

For more detailed tune-up instructions, see this post.

Lastly, Hyundai recommends you use 87 octane petrol. 91 octane is permitted, but will increase carbon build-up with long term use. Use only 87 if the car is running properly.

  • Good day, Thanks for your info! I've been using Petro Canada 91 octane with added detergents and 5w20 amsoil 6 month change for 8 years. Basic regular service for fluids,all belts,battery,brakes and coolant and is running well without any issues. Like your recommendation of just adding seafoam to the gas tank instead of playing with the intake using seafoam spray. Just got back from a fishing trip north of great lakes and added three cans of seafoam in a month doing 1700 k on this little 4 cylinder accent and noticing smoother engine operation and less buzz. I guess the old motto is, if it ain
    – jan
    Oct 10, 2017 at 15:43

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .