Finally changed my oil yesterday at 10K. After I drained the old oil, removed the filter, and spilled the usual amount of oil on the driveway and down my arm, I noticed that I had accidentally bought 3 qts of Mobil 1 10W30 and 1 qt of 5w30. So I mixed them rather than go out and buy more 5W30. In the manual it says that you can use 10W30, but that you should switch back to 5W30 with the next oil change. Any harm done mixing 2.7 qts of 10W30 and 1 qt of 5W30? I'm guessing that it is probably okay, but I'd be interested in your thoughts.
<div class='quotetop'>QUOTE(Seagull @ Mar 2 2007, 04:04 PM) [snapback]399021[/snapback]</div> No problems but be careful next time! 5W30 is better oil for winter use. I think winter is almost over in New Jersey and the mixture works well in spring and summer. In Finland the temperatures have been -20 to -25 degrees celcius (-4 to -13 fahrenheit) and I use Mobil Rally Formula 5W-50.
<div class='quotetop'>QUOTE(Heikki @ Mar 2 2007, 06:17 AM) [snapback]399026[/snapback]</div> Just curious. Why the 50 instead of 30? Dave M.
<div class='quotetop'>QUOTE(dmckinstry @ Mar 2 2007, 04:29 PM) [snapback]399032[/snapback]</div> Difference between 5W50 and 5W30 is small but the price is not. Mobil RF 5W50 is 25 € per 4 litres and 5W30 is about 45€ per 4 litres.
<div class='quotetop'>QUOTE(Heikki @ Mar 2 2007, 10:17 AM) [snapback]399026[/snapback]</div> Up until 10 days ago, we had lows down to -40 and highs of a brisk -30 C. At the very least, I prefer a 0W-30 for improved cold temperature performance and reliability. I'm running a 0W-20 with very good results. How is your fuel economy with the 5W-50? Some forum members who had their Prius accidently serviced with a 10W-40 or a 20W-50 reported substantial fuel economy loss. I run Mobil 1 0W-30 in summer and based on the used oil analysis, my motor wear is very, very low.
"How is your fuel economy with the 5W-50? Some forum members who had their Prius accidently serviced with a 10W-40 or a 20W-50 reported substantial fuel economy loss." Lifetime average is 4,77 litres/100 km.
<div class='quotetop'>QUOTE(Heikki @ Mar 5 2007, 06:00 AM) [snapback]400208[/snapback]</div> I did look into the Finnish Mobil site, and although I cannot speak Finnish, the technical data was clear enough. As is typical of Mobil in the past 6 years, they no longer publish detailed test data, such as cold temperature MRV or CCS. However they do publish HTHS, which is rated 4.22 mPa-s at +150 C. In contrast, the Mobil 1 0W-20 I use in my Prius is rated around 2.72 mPa-s. Mobil 1 0W-30 is rated 3.17 mPa-s at the same test temperature. The only cold weather data I could find is that Mobil rates the 5W-50 as having a -51 C pour point. That is a very good number, but it really doesn't tell us anything about cold temperature pumping at -40 C. Your grade of Mobil 1 5W-50 has many ACEA and factory approvals. It should work well to keep your motor clean.
I know this probably isn't a problem in Finland, at least until global warming kicks in, but could somebody in extreme heat run into a problem using the 5W-50 instead of the 5W-30? At some temperature point the oil would be beyond the weight (to 40 or even 50) that Toyota specifies (30).
Well, if you snoop around the Toyota Australia site, the service page has a general recommendation of a 20W-50 for conventional petrol cars and the many diesel utes and LandCruisers they sell. However, for VVT motors, they recommend a specific Toyota-branded 10W-30, nothing thicker I used to subscribe to the "thicker is better" mentality until I went to college, and spent a few years getting dirty with industrial process control. Usually, a *thinner* oil protects better, especially if frequent start/stop cycles are involved. Under extreme cold, a conventional thick oil can actually ruin a machine, as it runs "dry." I've attached a Toyota Australia pdf that has general recommendations for their local operating conditions.
