Trying to find relationships between markets is an ongoing task. Relationships change over time as markets change their focus, central banks change their policies, etc. The only constant is change.
Here I show the SP500 futures and Crude Oil futures on a daily continuation chart. The two markets were trading upwards together earlier this year as the commodity cyclicals continued to lead the stock markets higher.
Notice that in early August Crude Oil gapped up over $62 a barrel 2 days after the SP futures broke down. The SP futures contined down in a nice channel until Wednesday of last week when they broke up and out of the channel. Meanwhile, 2 days later on Friday of last week, Crude Oil futures broke down with a nice gap. $66.30 is important basis Oct for Crude. What the charts say is that if we see $62 again on Crude the SP will be up at the Aug highs of 1247. If Crude breaks below $62 then the stock market can be off to the races.
Something to watch in the days and weeks ahead.