Skip the auto shop - Our mechanics make house calls

Q: Will it hurt my motor to switch from synthetic oil to conventional oil?

asked by on

Will it hurt my motor to switch from synthetic oil to conventional oil. The mechanic who replaced my main seal said it wouldn't hurt but now my car smokes at cranking and slow idle it had no problems prior to the seal replacement

My car has 200000 miles.
My car has an automatic transmission.

A: Hi there. There are varied opinions about s...

Hi there. There are varied opinions about switching from synthetic oil to conventional oil. I am old school and believe you stick with the manufacturer’s recommendation for oil type. Nowadays, most conventional oils are a synthetic-blend. I believe BMW recommends synthetic oil.

Given your vehicle has 200,000 miles, it could be the engine’s oil consumption is somewhat normal. Replacing the rear main seal or switching oil type should not have caused the engine to start smoking.

If the smoke is black, it could be excessive fuel consumption. If the smoke is white with a bluish tint, it could be oil smoke. If the smoke is white and dissipates quickly, it could be condensation (cold) or coolant/antifreeze (warm). Switching back to synthetic oil may or may not help. If you would like to have another technician give the vehicle a second opinion, a certified professional from YourMechanic can come to your car’s location to inspect the smoking and idling problems so that this is properly resolved.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

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: When an engine is replaced should it include a new intake boot or air intake system? Or is that separate?

The intake hose and any external component of the engine is not included in an engine swap replacement unless it is listed to be replaced as a separate item to be replaced.

Q: Oil Change

Your Lexus GS430 takes one oil filter and requires 5.5 quarter including the oil filter. The manufacturer suggests using 5W-30 synthetic oil. I would recommend having an expert from YourMechanic come to your location to perform an oil change service...

Q: Speedometer is registering half speed

Hi there. Most of the time this is caused by a bad vehicle speed sensor. This is a common failure on this vehicle. When the sensor fails it either stops reading or it reads improperly. It can also be an...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.