Hi there,
As with most of questions of this nature, we cannot tell you if now is the time to sell the stock - that is a very personal decision that is based on your own investment profile. That includes your goals, risk tolerance, stage of life, etc. What we can say, is always circle back to why you bought it in the first place. Has the investment thesis changed? It sounds that based on your question, you might think it has. Does holding Suncor still fit with your investment profile?
If the thesis has changed, and it no longer fits an investor's profile - then is there another reason to hold it? Perhaps the investor is not seeing a better opportunity - ok to hold in this case until one comes up. However, if there is a better opportunity that is a better fit, then perhaps it may be time to sell and put those funds into that opportunity.
It is never an easy decision to sell a stock, particularly a historically strong one such as Suncor. I myself, hold Suncor and will be looking to exit my position once I identify the right opportunity. Although fossil fuels are going anywhere anytime soon, i prefer pipelines over producers in this environment. Until such time as I find that opportunity, I continue to hold.
Mat