AlpineRaven Posted July 31, 2005 Share Posted July 31, 2005 G'day fellas, I would like to start an discussion about Diesel Oils in Subaru Engines due noisy tappets & cleanness etc What would happen if we use Diesel Oils in NA & Turbo Petrol/Gasoline engines? Could Diesel Oils can ruin Catalytic Converter? Could Diesel Oils makes the engine to run hotter than normal oils? What is the Pros and Cons on using Diesel oils in Subarus (on NA & Turbos)? Thank you guys AP Quote Link to comment Share on other sites More sharing options...
nipper Posted July 31, 2005 Share Posted July 31, 2005 Interesting .... Diesel engines run at higher combustion pressure and temperitures then gasoline engines. the power pulse which is converted to ratational energy via the crankshaft is also much higher. Oil not only lubircates, but adds a cushion of oil to the crank journal to help protect it. I would have to assume that deisel engine oil is made to flow at these heavy loads, where normal engine oil would thin out and break down. My concern would be that the oil would never got hot enough to flow properly. Also if the engine is burning oil, if the spatk ignition eingine would fire a hot enough flame to burn the oil. Also deisel engine main bearings and crank journals are differnt from gasoline engines. If its an engine on its last legs, as a last what-the-hell try to get more life out of it, maybe try it. I would think you would shorten the life of the bearings. Also it may not be compatable with the oil filter. Quote Link to comment Share on other sites More sharing options...
friendly_jacek Posted July 31, 2005 Share Posted July 31, 2005 Most "diesel oils" in US are actually universal fleet oils with double diesel/gas (CH-4/SL) rating. If your car can take 15W40 API SL, then you can use diesel/gas CH-4/SL universal oils (delval, rotella, delo, etc.). I personally tried rotella synth 5W40 with good results in summer. Quote Link to comment Share on other sites More sharing options...
Setright Posted July 31, 2005 Share Posted July 31, 2005 Sure. There would be no real problems. The viscosity ratings are the same, so flow is not affected. The main advantage would the increase in dispersants found in the Diesel specific oil. They help keep the Diesel soot in suspension in the oil and therefore ferry it to the filter. The only disadvantange I can think of is fuel dilution of the oil. Perhaps the Diesel oil does NOT have additives to combat the attack of petrol. Therefore, a long drain interval - over 6k miles - might affect the lubrication performance of the Diesel oil. I have considered this myself and I will be running some Mobil Delvac through my engine soon, just to keep it clean. I'll bet it's a better and safer way than using an agressive aftermarket oil additive. Quote Link to comment Share on other sites More sharing options...
99obw Posted July 31, 2005 Share Posted July 31, 2005 I think I can answer two of your questions. Could Diesel Oils can ruin Catalytic Converter?I have read that the answer to this is yes. The metallic detergents in diesel oils can harm the cat if the engine burns a lot of oil. That hasn't stopped me from using it in the Subaru which burns a lot of oil, as the cats are about to fall off of the car from rust and I don't really care if I kill them. If your car doesn't burn much oil it shouldn't be an issue. With that said I should say that my diesel Jetta has a cat on it. Don't know what that means, but it has one, so I don't think the designers of the car were worried about it being damaged. It doesn't burn any oil, leaks it like crazy instead. Could Diesel Oils makes the engine to run hotter than normal oils? More energy is required to pump a thicker oil around an engine. That energy winds up heating a thicker oil to a higher temperature than a thinner oil would run. Depending on the engine and cooling system that might make the engine run hotter. I am running diesel oil, using Mobil 1 T&SUV 5w-40 (Delvac 1) in both gassers right now. No problems. I think it's interesting that a reputable company like Mobil is marketing a diesel oil with little to no modifications for gassers with cats. Some time in the next couple of months I will be posting the used oil analysis from my Jeep with the T&SUV in it, should be around 12k miles. I will post a link to the thread here on the USMB. Quote Link to comment Share on other sites More sharing options...
Losiho Posted July 31, 2005 Share Posted July 31, 2005 I just filled my Outback with Mobil Delvac 1 5W-40. So far it has been excellent. And I wouldn't hesitate to use a dual rated diesel engine oil in a gasoline car. Quote Link to comment Share on other sites More sharing options...
blitz Posted July 31, 2005 Share Posted July 31, 2005 Check the API certifications on the rear. If it doesn't list at least one of the following: SM, SL, SJ, then don't use it. Like friendly_jacek says, diesel: NO - mixed fleet: YES I have in front of me a 4 qt. jug of Pennzoil Long Life. The label states: "Maximum Protection For For Diesel And Gasoline Engines. The API donut lists the following certifications: API Service CI-4, CH-4, CF/SL The "S*.*" indicates the oil is certified for "Service" (4-stroke Passenger car). Bottom line: check the API certifications on the rear. If it doesn't list at least one of the following: SM, SL, SJ, then don't use it. Quote Link to comment Share on other sites More sharing options...
Hondasucks Posted July 31, 2005 Share Posted July 31, 2005 I was told that diesel oil works fine in a gas engine, but you don't want to put gas engine oil into a diesel engine. If the diesel oil says API service Cx but doesn't have an API service Sx on there, I wouldn't use it, but if it has both a C and an S service rating, then it will be fine (C = Compression Ignition, S = Spark Ignition) BUT make sure the Sx is what your car takes, but remember that it is superlative, meaning if you car takes, say API service SD, than you can run anything with an SD rating or higher, but not lower. Quote Link to comment Share on other sites More sharing options...
blitz Posted July 31, 2005 Share Posted July 31, 2005 Hondasucks, One detail correction: S = Service C = Commercial http://api-ep.api.org/filelibrary/API_MotorOilGuide_2004.pdf Quote Link to comment Share on other sites More sharing options...
NorthWet Posted July 31, 2005 Share Posted July 31, 2005 Hondasucks,One detail correction: S = Service C = Commercial http://api-ep.api.org/filelibrary/API_MotorOilGuide_2004.pdf Gee, in the old days they used to put on the containers SI-x and CI-x... *Edit - And, oh, that PDF gives mixed information as to the meaning. As blitz stated, it does indeed equate S with Service and C with commerical. But it also says the S is gasoline and C is diesel. Plus it lists CI in its ratings. My guess it that the API ratings have "evolved" and the letters are now just letters. Sort of like the AARP used to be for "Retired People", but now the letters AARP are just letters without any meaning (per AARP Prez). As others have stated, diesel oil is not inherently "thicker", and can't be if it is compared with any other oil with the same viscosity rating. The API PDF does mention that it has a higher resistance to viscosity loss caused by shear in a diesel engine. -end edit * Quote Link to comment Share on other sites More sharing options...
Bmm001 Posted July 31, 2005 Share Posted July 31, 2005 The Subaru garage we take all our cars to always uses 15W-40, citing higher levels of detergent, better overall protection, and less piston slap as their reasons. They've been working on Subarus for over 20 years and used this oil with no problems, so if it works for them, it works for me. I also noticed that our Subaru dealer used 15W40 for about the first 2 years we've had our '98 before they switched to Mobil (they used to use Castrol). Brian M. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.