It's fine, most HDEO's also carry an SM(gasoline) rating as well. T6 is a fine oil, I think you'll be happy with it. The T6 is also a "low ash" formula.
Here's a little bit from Shell's website as well;
SM oil will work just fine, for example, in a car that specifies SH. But an SG won?t. You?ll also need the correct viscosity grade. Most modern gasoline engines use 5W-30 or 10W-30 multigrade oils. The "5W" and "10W" part of the viscosity grades help maintain better fuel economy and good cold temperature performance. You can use heavier oils ? but if your vehicle is still under warranty, check first with the engine manufacturer.
If your personal vehicle runs on gasoline and is no longer under warranty, then you?ll need a ?universal? oil (such as ROTELLA T 15W-40) that?s designed to serve both diesel and gasoline engines. Check the label for the API SERVICE designation. Be careful because some premium oils are for diesel use only.