mixing stuff.
 

These may seem like simple questions but there may be other factors to consider that I don't know about. 1)If I mix equal amounts of 87 octane gasoline and 93 octane gasoline will I get 90 octane gasoline? The reason I ask is that in my area mixing the 87 and 93 is cheaper than buying 89 octane (plus it is a point higher). 2) Will mixing 10-30 motor oil and 15-50 motor oil (same brand and type) give me 12.5-40 oil? The reason I ask this is because I have a lot of 15-50 I don't want to use. Thanks for any input.

Yes, in terms of the same brand of gas a 50/ 50 mixture will average out.

Your oil question is a bit hard to say since the additive package between the two might be different.

It's a little known secret that there is no 89 or midrange octane delivered to gas stations. The midrange octane is created at the station by mixing the regular and premium fuels from the tanks. The cost of having a third separate tank system is too expensive in today's marketplace.

As far as this "little known secret" goes, the secret isn't accurate.

Formerly I was a driver that drove fuel tanker for a few years before I retired, this statement isn't entirely true. While some stations do mix the premium and regular fuel at the pumps to make the mid grade, there are also many stations that do have 3 gasoline storage tanks, and the mid grade fuel is blended at the loading racks as it goes into the tanker. It isn't cut and dried that all stations don't have a third tank for mid grade, and they're blending it onsite. The tanker usually has 4 compartments so they can transport 3 grades of gasoline, as well as diesel.

The code for underground mid grade fill cap is a blue background with a white cross in the center. The premium is a red background with a white cross in the center. Regular fuel is a white background with a black cross in the center. The fill markings for gasoline are on the far left.

https://i.ibb.co/FqJ4h6xL/API-Codes-4089960066.jpg

Can't believe everything you read on the internet.

Concerning mixing the motor oils. You might want to go on the motor oil web site for whatever brand you have and look up the Product Data Sheets for each of the oils. If they look the same or very close, you can likely mix them without any issues.

That pretty much answered the gasoline question. I guess I'll have to do a little more research on the oil.

Here’s a handy chart for mixing race gas.

Steve25, could you repost that chart? I can't make out the heading on the left because of the glare. It would also be nice to read the text below the chart. This chart would answer some of the questions I have as I have been mixing gas for my 67 GTO. Thanks!

Here’s a clearer photo.

Thank you!