I recently had to take my 2004 Prius in for emergency maintenance because of a soft squealing that had been happening for the last few days when the car was at speed (pretty much anything over 10mph). I decided, since my maintenance required warning light was on, that I might as well also get an oil change. After paying for the maintenance (some rocks got stuck in my brake pads), I noticed an odd little line on my invoice.
The maintenance code on the oil change line indicated an oil weight of 0W-40, which seemed like an odd weight at the time (but apparently does exist). I went back to my maintenance lead and asked what weight was used, and he said that it was, in fact, 0W-40. He said that all Toyota cars use this without any problems. This is patently wrong, since the Prius requires 5W-30 for proper operation (and waving the owner’s manual in this guy’s face got him to realize this). However, this dealership only carries 0W-40! He made a special arrangement for me to come back this morning and get the oil change redone with the proper weight, which has now been done.
What’s the point of this story? According to fueleconomy.gov, it’s imperative to ensure that your car is using the proper weight of oil for best operation. There are, in fact, cars that will not operate at all with the wrong oil weight (and the wrong oil weight can also severely damage some engines). Do you know the proper oil weight for your car? Are you sure your dealership consistently uses that weight and isn’t overfilling your oil? Most dealers pump straight from a barrel, which makes it very hard to prevent overfilling. I verified a practice today that I had done the first time I did an oil change – bring your own oil and insist that they put the correct amount in. I’ll never make the mistake of not buying and bringing my own oil in again!