My engine stopped on highway and i could not accelerate...What could the issue?

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No signs at all. and i just changed the oil with 5 litres of toyota oil and oil filter barely 48 hrs ago. No leakage of oil under the engine. I noticed the oil was almost dry as the time the engine stopped on highway.. i thought the oil did not guage well and I added more 4 litres of toyota oil to it. Still it did not guage. in total, i have added 9 litres of oil. the engine did not start. Please what could be the problem?