Oil Blending - How to use up my 10W40 15W40 stash?

[uart]

This one of those "I don't really like blending, but ..." questions.

I've got a 2005 Prius and a 2005 Mazda 2. In the past I've always used 5W30 (year round) in the Prius and 10W40 in the Mazda. The owners manuals here specify a fairly broad range of allowable viscosity and the climate is mild/warm.

Now I'd like to go a bit thinner in the Mazda., so last oil change I filler her with about a 50/50 mix of 5W30 and 10W40. No real science behind the blending, just used what I had on hand. The 5W30 was Caltex C3 synthetic (see link) and the other one was the plain 10W40 version of Castrol Magnetec.

Now I'm having second thoughts about the wisdom of making random 50/50 blends like this. But if not then how am I gonna ever use up my 30 qt stash of 10W40 / 15W40?

LOL this has gotta be a text book case of why it's not always a good idea to stash too much oil.

Oils:
http://www.caltex.com.au/ProductsAndServices/Pages/ProductDescription.aspx?ID=1800

http://www.castrol.com/castrol/productdetailmin.do?categoryId=8000009&contentId=7076245

 

[LineArrayNut]

do they even have 0w-20 in Oz? Do you have any real winter? I like blending, lol!

 

[supercity]

The 5w30 is A3 rated so the viscosity is not that far off the other 40 grades.

 

[uart]

Originally Posted By: LineArrayNut
do they even have 0w-20 in Oz? Do you have any real winter? I like blending, lol!

No, we don't really have readily available 0W20 here. Also most of the time the daytime winter temperatures are over 50F. I just want to thin my 10W40 down a little bit with 5W30.

Originally Posted By: supercity
The 5w30 is A3 rated so the viscosity is not that far off the other 40 grades.

Yeah it's a pretty robust 5W30, but still thinner than the 10W40 magnatec.

So here are my other options for blending that 10W40 Magnatec.

1. I've already got some Valvoline DuraBlend 5W30 that I sometimes use for the Prius in winter. I could blend that with the Magnatec.

2. They've only recently started selling 5W30 "Fuelsaver" Magnatec here, and it's a pretty thin 5W30. I haven't tried it yet because it's pricey (double the price of the 10W40 stuff) and it doesn't list any specs apart from just SN GF4. That's why I've been preferring to buy DuraBlend for a nice thin semisynth, as it's dexos1 rated and cheaper than the 5W30 Magnatec.

So should I go by some overpriced Magnatec 5W30 "fuelsaver" to blend with, or should I try a blend with 5W30 Valvoline Durablend to thin down my 10W40 stuff?

 

[gfh77665]

Originally Posted By: uart
I've always used 10W40 in the Mazda. The owners manuals here specify a fairly broad range of allowable viscosity and the climate is mild/warm.

Now I'd like to go a bit thinner in the Mazda.,


I would not buy more & blend. Just use it up, 30 qts won't last that long. If it worked OK in the past, it won't hurt now. After the 30 qts are gone, then just buy excatly what you want. Blending will just streach out how long you have to deal with the 10-40.

 

[Shannow]

Rather than buying something else, to make something that you don't really want, cut your losses and put the magnatec on Gumtree at 2/3 the Repco/Supercheap price. $30 for 5L say.

I'd hope that they sell faster than you would otherwaise draw down the stash.

Then you can fill up with Calibre 5W-30 (Caltex C3) for $8/l, or Atlantic (MOBIL Singapore base stocks and Lubrizol adds)

Or go completely over the edge, and get some Caltex 5W-20in a 20L drum (3 different 5W-20s, all in "professional") and make a blend of significant percentages of thinner stuff.

 

[uart]

Originally Posted By: Shannow
Rather than buying something else, to make something that you don't really want, cut your losses and put the magnatec on Gumtree at 2/3 the Repco/Supercheap price. $30 for 5L say.

I'd hope that they sell faster than you would otherwaise draw down the stash.

Then you can fill up with Calibre 5W-30 (Caltex C3) for $8/l, or Atlantic (MOBIL Singapore base stocks and Lubrizol adds)

That Atlantic stuff looks interesting, but I don't think I've seen it anywhere that I shop. Who sells it?

At the moment I've got plenty of 5W30 to run in both cars, but I'm still in two minds about whether to blend-away my 10W40 or not.

I was going to use the 10W40 for summer changes and the 5W30 in winter, but these days the Mazda doesn't get driven much so I'm only doing an annual change.

I think I'll try 2L of durablend 5w30 and 2L of magnatec 10W40 for my next oil change. I'm an incurable blender, I can't help myself.