A routine oil change turned into a troubling highway drive for the owner of a 2018 Toyota RAV4 Hybrid after the SUV began producing white smoke, losing acceleration, and triggering its check engine light shortly after leaving a repair shop.
The driver first noticed white smoke coming from the tailpipe while accelerating on the freeway. The SUV later struggled to exceed 60 mph, even with the accelerator pressed down.
The repair shop sent mechanics to inspect the Toyota. They reportedly found nothing wrong with the oil level or the components involved in the service, but a diagnostic scan revealed misfires affecting two engine cylinders.
The experience was described in an October 9 Reddit post on r/MechanicAdvice by a friend of the vehicle’s owner. After initially questioning whether the problems were related to the oil change, the poster later reported discovering that the engine had been overfilled.
Mechanics Check SUV
Spark plugs issue after oil change?
by
u/generalraccoons in
MechanicAdvice
The owner had taken the RAV4 Hybrid to a mechanic they regularly used for an oil change. Trouble began almost immediately afterward.
After the driver contacted the shop from the road, employees arrived to inspect the SUV. They reported that the drain plug, oil filter, and oil cap were properly installed. They also insisted the engine contained the correct amount of oil.
A diagnostic scan revealed misfires in cylinders three and four. When the owner asked whether the mechanics had touched those components during the oil change, they reportedly said they had not.
One mechanic acknowledged spilling some oil onto the exhaust system, which could explain smoke from beneath the vehicle. However, that explanation did not account for the loss of engine power.
The mechanics attempted to isolate the misfires by moving the cylinder-three spark plug to cylinder one and swapping the cylinder-four ignition coil with the one in cylinder two.
A subsequent test drive produced no additional diagnostic codes. The shop did not charge the owner for the roadside inspection.
Warning Light Returns
The apparent improvement did not last.
The following day, the owner drove approximately 30 miles without noticeable trouble. Near the end of the trip, the check engine light flashed approximately six times while the Toyota was traveling on the freeway.
The Reddit poster planned to obtain a diagnostic scanner to investigate the recurring warning.
Before the oil change, the owner had reportedly driven the SUV for years without experiencing comparable acceleration problems or check engine warnings.
Overfilled Oil Identified
A commenter suggested that the trouble could be connected to the recent oil change and identified two possible causes.
One involved using an incorrect oil specification that could interfere with the engine’s variable valve timing system. The other involved excessive oil entering the combustion chambers through the positive crankcase ventilation system, potentially contaminating the spark plugs.
The commenter recommended inspecting the spark plugs for oil residue.
Several days later, the original poster returned with an update.
“They overfilled the oil!” the poster wrote, thanking the commenter for the suggestion.
An overfilled engine can experience oil aeration and contamination of the intake system. Those problems can interfere with normal engine operation, although the post did not establish the precise cause of the Toyota’s misfires.
The poster did not disclose how much excess oil had been added or how the overfill was discovered. No final repair report was provided, and it remains unclear whether correcting the oil level resolved the SUV’s acceleration problems and recurring check engine warning.