Q: Bad mileage & strong gas smell in dipstick/oil pan - 1996 Nissan 300ZX

asked by on

I started checking out my car because I was getting very bad mileage. When checking the oil dipstick, there was a strong smell, distinctive of gasoline. I removed the oil pan and the smell was even worse. I’ve been told many, many things by other people, but I don’t want to guess and replace things until I’m able to figure out what is wrong with it and fix it the first time. My mechanic tells me that he can’t and won’t diagnose it manually. I’ve been told different things: it’s the fuel dampener, the fuel regulator, piston rings, fuel injectors, engine valves not seated right, malfunctioning engine temperature regulator/thermostat, leak in the fuel line… In your professional opinion, what is the problem?

Okay, so usually the answer to problems are usually hidden in the fine details. The whole reason you started noticing a problem was the gas mileage. If this was my car, I would be thinking that I have a fuel injector stuck open or for some other reason, the engine is letting more fuel be used than is neccessary. Piston rings are not air or liquid tight. If you have an incredibly rich mixture (more fuel than you can burn) it will make the oil smell like gas, but that doesn’t mean anything is wrong with the rings necessarily. A leak in the fuel line would explain the mileage but not the oil smelling like gas. The only thing that explains both symptoms is that the extra fuel is entering the combustion chamber. I am betting it is something related to the system regulating fuel into the combustion chamber. I wish I could stick my finger on just one thing, but I hope I helped narrow it down a bit. Yet, if you would like, a certified technician from YourMechanic can come to your home or office, and definitively diagnose your poor gas mileage issue.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Bad mileage & strong gas smell in dipstick/oil pan - 1996 Nissan 300ZX

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: My car reduced speed and increase at the same time even on the motion

Hi there. The description you have given, appears to be a fuel starvation issue. Surging and bucking upon acceleration could be a fuel pump problem. Not knowing what year your Toyota is, it may have an external fuel filter that...

Q: No pressure after the FPR

The fuel pressure regulator will regulate the fuel pressure by allowing fuel to return back to the fuel tank if the pressure gets too high. If the fuel pump never produces enough pressure and volume of fuel to run the...

Q: Exhaust smoke smells like gas or burning oil.

Hi there. The smoke coming out of your exhaust is most likely oil being burned through your engine. The oil gets into the cylinder by a few ways. The first way is for the oil to get by the oil...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...