Oil dilution

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None of our vehicles have Direct Injection , but wondering about oil dilution by gasoline . If a person was doing mostly highway miles , would the heat help evaporate the gasoline out of the oil ? Thanks , :-0
 
Still asking about dilution in DI engines, or are you wondering about non-DI? In port-injected engines there's gotta be something bad wrong with the fuel system, or a ton of sub-operating-temperature driving for fuel in the oil to become a problem. In DI, obviously, it's of more concern either way but highway miles minimize it purely from the basic concepts of more efficient combustion under those conditions.
 
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Originally Posted By: WyrTwister
None of our vehicles have Direct Injection , but wondering about oil dilution by gasoline . If a person was doing mostly highway miles , would the heat help evaporate the gasoline out of the oil ? Thanks , :-0
Yes
 
Yes. EFI is very stingy with excess fuel. In a decently maintained engine fuel dilution is less than 1% according to the oil analysis reports.
 
A long, long time ago cars survived with carburetors that dumped excess gasoline into the intake system because of less than precise fuel metering often opting for too rich to allow the engine to run smoothly. It's true. And the gasoline mixed in the oil would evaporate as the engine heated up the next time it was driven. Oil change intervals were 3K miles and before that 2K miles and that worked well enough to take care of the dilution. The problem with trying to figure out if fuel dilution today is really a problem is that you start with lab testing that may be trend accurate and not sample accurate. This means that an error on a test is about the same error on every test so the trend is more accurate than any single test. More than one test would be good. Next is the idea that the lab test is a snapshot and does not reflect an average or capture the highest percentage. There might also be periods of driving where the percentage is really bad but clears up as the workload increases. In other words, you might have a problem that would never be detected by lab work. You have to speculate that there might be a problem. What we need is some help from BITOG members to figure out a realistic plan for determining the extent of fuel dilution that might include driving conditions, driver habits, engine configuration and lab results. Next would be, how to reduce the problem knowing that eliminating the problem completely is not feasible. The solution might include modification of driving habits, oil selection, oil change intervals, an occasional Italian tuneup, gasoline additives and lab work. Only those OCD owners would even think about something like this but this is what makes BITOG the Website that it is today.
 
I think part of the issue with fuel dilution in modern DI/TGDI engines is that the dilution is not an accident and doesn't only occur on start-up. To prevent LSPI and respond to regular spark knock, fuel injection timing and richness is adjusted, which can lead to fuel dilution even during constant Interstate driving. So, even if some of the fuel is evaporated away, it is replaced by fresh dilution. And once fuel mixes with engine oil it is surprisingly difficult to get rid of. Many gasoline components have evaporation temperatures higher than typical sump temperatures, so a good part of it will stay around for the balance of the OCI. If one wanted to be cynical, it would be easy to assume OEMs are avoiding catastrophic engine damage during warranty (LSPI) by sacrificing long-term durability caused by fuel dilution (out of warranty). And while it's true that fuel dilution was probably common in the carburetor days, engine durability wasn't so great then either. There are so many variables it seems all we can do it wait and see how DI/TGDI engines age. And wait and see if there are a rash of reprograms once dexos1Gen2 oils or ILSAC equivalents are the only oils available.
 
I have heard EFI is one of the reasons gas engines seem to last longer than they did in my youth .
 
[quote=OneEyeJack]A long, long time ago cars survived with carburetors that dumped excess gasoline into the intake system because of less than precise fuel metering often opting for too rich to allow the engine to run smoothly. It's true. And the gasoline mixed in the oil would evaporate as the engine heated up the next time it was driven. Oil change intervals were 3K miles and before that 2K miles and that worked well enough to take care of the dilution. The problem with trying to figure out if fuel dilution today is really a problem is that you start with lab testing that may be trend accurate and not sample accurate. This means that an error on a test is about the same error on every test so the trend is more accurate than any single test. More than one test would be good. Next is the idea that the lab test is a snapshot and does not reflect an average or capture the highest percentage. There might also be periods of driving where the percentage is really bad but clears up as the workload increases. In other words, you might have a problem that would never be detected by lab work. You have to speculate that there might be a problem. What we need is some help from BITOG members to figure out a realistic plan for determining the extent of fuel dilution that might include driving conditions, driver habits, engine configuration and lab results. Next would be, how to reduce the problem knowing that eliminating the problem completely is not feasible. The solution might include modification of driving habits, oil selection, oil change intervals, an occasional Italian tuneup, gasoline additives and lab work. Only those OCD owners would even think about something like this but this is what makes BITOG the Website that it is today. [quote] thumbsup
 
Originally Posted By: WyrTwister
I have heard EFI is one of the reasons gas engines seem to last longer than they did in my youth .
When all the gas engines ran carburetors .
 
I grew up with cars with carbs . I hated the automatic chokes , always too much or not enough . And , often they would stick , not opening up all the way . After the engine had warmed up . 1989 Chevy Cavalier was our first new car ( bought at the end of the model year ) and first car with Electric Fuel Injection . At that time period , my Wife was working in the kitchen , at one of the school cafaterias . She left for work in the AM , earlier than I did . In the cold of winter , often I had to get up and get dressed & go out & start the car for her & keep it running long enough to warm up enough to keep it running . The Cavalier , with Throttle Body Injection , summer or winter , she went out to the car , inserted the key and with in 1 or 2 revolutions , it started & it would continue to run . I have no experience with direct injection and am not in a hurry to experience it . If or when we buy a car with direct injection , hopefully they will have the bugs worked out of it . Happy Thanksgiving and the best to you all , :-)
 
Originally Posted By: WyrTwister
I grew up with cars with carbs . I hated the automatic chokes , always too much or not enough . And , often they would stick , not opening up all the way . After the engine had warmed up . 1989 Chevy Cavalier was our first new car ( bought at the end of the model year ) and first car with Electric Fuel Injection . At that time period , my Wife was working in the kitchen , at one of the school cafaterias . She left for work in the AM , earlier than I did . In the cold of winter , often I had to get up and get dressed & go out & start the car for her & keep it running long enough to warm up enough to keep it running . The Cavalier , with Throttle Body Injection , summer or winter , she went out to the car , inserted the key and with in 1 or 2 revolutions , it started & it would continue to run . I have no experience with direct injection and am not in a hurry to experience it . If or when we buy a car with direct injection , hopefully they will have the bugs worked out of it . Happy Thanksgiving and the best to you all , :-)
Amen, brother. Last car with a carb. 1980 Chevy Citation. Horrible in the winter. Next car, 1985 VW Golf with FI. Never a hiccup.
 
As answered, it somewhat depends on driving habits and oil change interval, etc. Also has to do with condition of carb. Worn throttle (butterfly) bushings can cause the mixture to run rich, as can poorly set up carbs. SU carbs can be set up wrong (float level too high) so they will always gulp too much fuel no matter how you try and adjust mixture. Yes, driving the car on highway or well warmed up for long drives can evaporate off the gas if the rich problem is minor or just happens occasionally when too much choke used too long. How do you tell if the carb is dramatically out of tune or otherwise dumping to much fuel while seeming to run well? Use the sniff test and look at your spark plugs. If you are satisfied you drive the car enough and in conditions that should "boil" off the gasoline from the oil, and yet the oil still smells like somebody dumped gasoline in the sump, then your carbs are dumping too much fuel in there and no amount of running around will get rid of it. Sure fire test is to change the oil and filter element, then go for a long highway drive and park it in the garage after, and if the oil stinks like gasoline when you check it in the morning you got a carb problem.
 
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