Could it be related to lower US refinery runs so far this year?

Last time I checked TWIP (This Week In Petroleum) I found that cumulative refinery runs were approximately 55 million barells behind the same periode for 2005.

Partly explains the build in crude storage.

Gasoline imports are up 20 % (or 200 kb/d) on a year on year basis.

Gasoline storage draws are presently high, and even if refinery runs on average is running only approx. 500 kb/d below 2005, it suggests to me that refineries are turning out less gasoline.

Could this be due refineries using heavier oil and/or lack of lighter oil like Brent and WTI?

SORRY LAST SENTENCE SHOULD READ;

Could this be due to refineries now using heavier oils and/or insufficient supplies of lighter crudes like Brent and/or WTI?

This could say something about present availability of sweet crudes.

US oil production according to TWIP is down approx. 400 kb/d relative 2005.

It's primarily because some refineries are still down from the hurricane. We have never gotten back to full capacity. See this graph for refinery utilization, and you can see that we haven't recovered:

http://www.petrostrategies.org/Graphs/refineryutilization.html

RR

Sulfur content is about the same as 6 years ago.

The same with viscosity

Clearly since 1985 there has been a deterioration in both areas - how significant this is, is unclear.

Thanks for the link to data on refinery inputs. What I think that this illustrates is that there was been limited [if any] improvement in the ability of U.S. refineries to handle higher amounts of heavy / sour crudes.

If production is shifting toward these heavier sour grades, "Houston we have a problem" [an appropriate city from a quote coming completely out of context. Depending on your degree of faith in the U.S. Government feel free to substitute "Washington" for "Houston".] :-)